<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:ff57c454-e64f-485b-9b31-3a69f9dfb008,g:ec5882c7-0c69-4ea7-94a1-72be941f6e5a-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.supernus.com/role/CondensedConsolidatedStatementsofEarningsLoss" xlink:type="simple" xlink:href="supn-20240930.xsd#CondensedConsolidatedStatementsofEarningsLoss"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/CondensedConsolidatedStatementsofEarningsLoss" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_7cd02a39-0952-4db9-a79b-315277146565" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_StatementTable_7cd02a39-0952-4db9-a79b-315277146565" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_1cd45167-a1aa-409d-aad7-7395239903c2" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_7cd02a39-0952-4db9-a79b-315277146565" xlink:to="loc_srt_ProductOrServiceAxis_1cd45167-a1aa-409d-aad7-7395239903c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_1cd45167-a1aa-409d-aad7-7395239903c2_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_1cd45167-a1aa-409d-aad7-7395239903c2" xlink:to="loc_srt_ProductsAndServicesDomain_1cd45167-a1aa-409d-aad7-7395239903c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_83a76afa-dba1-4c5d-9bf9-fc5033ccfe61" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_1cd45167-a1aa-409d-aad7-7395239903c2" xlink:to="loc_srt_ProductsAndServicesDomain_83a76afa-dba1-4c5d-9bf9-fc5033ccfe61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_025425e7-df37-411d-ad7f-dabe7c028161" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_83a76afa-dba1-4c5d-9bf9-fc5033ccfe61" xlink:to="loc_us-gaap_ProductMember_025425e7-df37-411d-ad7f-dabe7c028161" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_RoyaltyLicenseAndOtherRevenueMember_2fa0947c-4698-4053-9f9c-e61c5700d5b7" xlink:href="supn-20240930.xsd#supn_RoyaltyLicenseAndOtherRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_83a76afa-dba1-4c5d-9bf9-fc5033ccfe61" xlink:to="loc_supn_RoyaltyLicenseAndOtherRevenueMember_2fa0947c-4698-4053-9f9c-e61c5700d5b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_6216b2ed-3330-4541-a58c-54b755d8f3d1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_RevenuesAbstract_6216b2ed-3330-4541-a58c-54b755d8f3d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_843bc0d9-f7d0-49e4-bdfb-fc9e7a2c8c97" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_6216b2ed-3330-4541-a58c-54b755d8f3d1" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_843bc0d9-f7d0-49e4-bdfb-fc9e7a2c8c97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_cd000d53-b3a6-4e28-b4c7-188bed9fbb49" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_cd000d53-b3a6-4e28-b4c7-188bed9fbb49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_8f89de90-3370-4488-8130-b34789951fef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_cd000d53-b3a6-4e28-b4c7-188bed9fbb49" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_8f89de90-3370-4488-8130-b34789951fef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_8416c997-583b-4587-aa5f-f1a061713b0f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_cd000d53-b3a6-4e28-b4c7-188bed9fbb49" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_8416c997-583b-4587-aa5f-f1a061713b0f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_6e290ee8-3fba-41d7-9a56-07ed4d2bf823" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_cd000d53-b3a6-4e28-b4c7-188bed9fbb49" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_6e290ee8-3fba-41d7-9a56-07ed4d2bf823" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_3743a4ab-9ddc-4804-93a3-e04c6c98edb2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_cd000d53-b3a6-4e28-b4c7-188bed9fbb49" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_3743a4ab-9ddc-4804-93a3-e04c6c98edb2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_1d252071-ad2b-4986-8761-2aa4994552e0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_cd000d53-b3a6-4e28-b4c7-188bed9fbb49" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_1d252071-ad2b-4986-8761-2aa4994552e0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_96f0a1ea-9a9e-4ea8-9578-1776825a46f1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_cd000d53-b3a6-4e28-b4c7-188bed9fbb49" xlink:to="loc_us-gaap_CostsAndExpenses_96f0a1ea-9a9e-4ea8-9578-1776825a46f1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_5fb220ab-87bc-4a80-a748-7fdbe53eb96d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_OperatingIncomeLoss_5fb220ab-87bc-4a80-a748-7fdbe53eb96d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_9642490c-5dae-4cb3-b896-fe3025ca074d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_9642490c-5dae-4cb3-b896-fe3025ca074d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_ed0e19fe-5ead-4bcb-acae-246c9d9ff8ce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_9642490c-5dae-4cb3-b896-fe3025ca074d" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_ed0e19fe-5ead-4bcb-acae-246c9d9ff8ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_b679ac29-310b-4ee1-b885-a69a5e4120f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_9642490c-5dae-4cb3-b896-fe3025ca074d" xlink:to="loc_us-gaap_InterestExpenseNonoperating_b679ac29-310b-4ee1-b885-a69a5e4120f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_7bd7c4b8-8637-486f-afe8-018533affac0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_9642490c-5dae-4cb3-b896-fe3025ca074d" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_7bd7c4b8-8637-486f-afe8-018533affac0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_da65f0e3-7727-4d53-8327-5ef1d94c65cc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_da65f0e3-7727-4d53-8327-5ef1d94c65cc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_75a3c0b8-a892-47af-b97e-61c9237985f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_75a3c0b8-a892-47af-b97e-61c9237985f3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_e643053c-5681-4f72-b73f-3da0adb7bf1f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_NetIncomeLoss_e643053c-5681-4f72-b73f-3da0adb7bf1f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_EPSBasicAndDilutedAbstract_5b7f4b0a-0766-4949-b435-1a9ac4b12c98" xlink:href="supn-20240930.xsd#supn_EPSBasicAndDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_supn_EPSBasicAndDilutedAbstract_5b7f4b0a-0766-4949-b435-1a9ac4b12c98" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_882e1f09-b202-405f-b68c-502713f1a355" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_EPSBasicAndDilutedAbstract_5b7f4b0a-0766-4949-b435-1a9ac4b12c98" xlink:to="loc_us-gaap_EarningsPerShareBasic_882e1f09-b202-405f-b68c-502713f1a355" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_d24aee8a-846e-40e8-8db0-1d8d1ff1e87a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_EPSBasicAndDilutedAbstract_5b7f4b0a-0766-4949-b435-1a9ac4b12c98" xlink:to="loc_us-gaap_EarningsPerShareDiluted_d24aee8a-846e-40e8-8db0-1d8d1ff1e87a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_11852f03-4ffe-45ba-a0c0-1ba847dcad8b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4cd86a89-ff41-4e29-88bb-634b9e105c57" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_11852f03-4ffe-45ba-a0c0-1ba847dcad8b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_22c1588c-75f2-4f87-85d6-5c531de26115" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_11852f03-4ffe-45ba-a0c0-1ba847dcad8b" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_22c1588c-75f2-4f87-85d6-5c531de26115" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_b4846c9e-cd31-4f37-b587-465866849efb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_11852f03-4ffe-45ba-a0c0-1ba847dcad8b" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_b4846c9e-cd31-4f37-b587-465866849efb" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/CondensedConsolidatedStatementsofChangesinStockholdersEquity" xlink:type="simple" xlink:href="supn-20240930.xsd#CondensedConsolidatedStatementsofChangesinStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/CondensedConsolidatedStatementsofChangesinStockholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_ba99a144-af99-45ea-830d-977c219167ca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_eee0178a-bd0e-448c-8e8e-04f7c3fcaed3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_ba99a144-af99-45ea-830d-977c219167ca" xlink:to="loc_us-gaap_StatementTable_eee0178a-bd0e-448c-8e8e-04f7c3fcaed3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_5763d09b-e1d4-42a2-9a45-f1cfec21d254" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_eee0178a-bd0e-448c-8e8e-04f7c3fcaed3" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_5763d09b-e1d4-42a2-9a45-f1cfec21d254" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_5763d09b-e1d4-42a2-9a45-f1cfec21d254_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_5763d09b-e1d4-42a2-9a45-f1cfec21d254" xlink:to="loc_us-gaap_EquityComponentDomain_5763d09b-e1d4-42a2-9a45-f1cfec21d254_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_3c7da4f8-e0e6-494b-9571-46a19905cb67" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_5763d09b-e1d4-42a2-9a45-f1cfec21d254" xlink:to="loc_us-gaap_EquityComponentDomain_3c7da4f8-e0e6-494b-9571-46a19905cb67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_76e3402f-0a70-46f2-87d4-c7a0bdac7f5e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3c7da4f8-e0e6-494b-9571-46a19905cb67" xlink:to="loc_us-gaap_CommonStockMember_76e3402f-0a70-46f2-87d4-c7a0bdac7f5e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_f4a8e208-2de5-4f6d-b5a7-188296d93c24" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3c7da4f8-e0e6-494b-9571-46a19905cb67" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_f4a8e208-2de5-4f6d-b5a7-188296d93c24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_849d8949-0799-4427-94a3-88808901856f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3c7da4f8-e0e6-494b-9571-46a19905cb67" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_849d8949-0799-4427-94a3-88808901856f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_b070c877-2234-4e82-98be-0e8b5e039f82" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3c7da4f8-e0e6-494b-9571-46a19905cb67" xlink:to="loc_us-gaap_RetainedEarningsMember_b070c877-2234-4e82-98be-0e8b5e039f82" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ba99a144-af99-45ea-830d-977c219167ca" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_c92b6e0a-ea6f-425c-8adb-ab613c3a0545" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_c92b6e0a-ea6f-425c-8adb-ab613c3a0545" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_47ff422e-e70e-4426-a1ce-4ca3263cbccd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:to="loc_us-gaap_StockholdersEquity_47ff422e-e70e-4426-a1ce-4ca3263cbccd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_46c7074d-9480-47c4-b0cc-7e92f7f9166c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_46c7074d-9480-47c4-b0cc-7e92f7f9166c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_c4159db6-7bda-48c7-bccb-016a503c083e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_c4159db6-7bda-48c7-bccb-016a503c083e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_99d262be-4266-4cb2-85ed-94441c211c96" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_99d262be-4266-4cb2-85ed-94441c211c96" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_b1483733-4004-40c1-928e-3b870f56e409" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:to="loc_us-gaap_NetIncomeLoss_b1483733-4004-40c1-928e-3b870f56e409" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_f1d25225-51c4-4d06-a72e-07810cdab8bc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d8b1f2ed-7f17-4458-b451-8691e3bb5c64" xlink:to="loc_us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_f1d25225-51c4-4d06-a72e-07810cdab8bc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_7ca386bb-45bc-4807-9411-b05cd82cd28c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1b6cb4ef-02a3-48d7-b9ed-a69d06590c01" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/DisaggregatedRevenuesDisaggregationofRevenuesDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#DisaggregatedRevenuesDisaggregationofRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/DisaggregatedRevenuesDisaggregationofRevenuesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_63937737-f6ed-46a4-b79e-b1a8329648f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_29c177d8-5bc6-4adb-ab3a-3059522ae8b6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_63937737-f6ed-46a4-b79e-b1a8329648f4" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_29c177d8-5bc6-4adb-ab3a-3059522ae8b6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_3b421b5b-8186-4775-8ba7-e695854aba70" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_29c177d8-5bc6-4adb-ab3a-3059522ae8b6" xlink:to="loc_srt_ProductOrServiceAxis_3b421b5b-8186-4775-8ba7-e695854aba70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_3b421b5b-8186-4775-8ba7-e695854aba70_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_3b421b5b-8186-4775-8ba7-e695854aba70" xlink:to="loc_srt_ProductsAndServicesDomain_3b421b5b-8186-4775-8ba7-e695854aba70_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_1001a08a-7a6b-45f3-abda-16cb69f0a825" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_3b421b5b-8186-4775-8ba7-e695854aba70" xlink:to="loc_srt_ProductsAndServicesDomain_1001a08a-7a6b-45f3-abda-16cb69f0a825" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_c7174df2-3220-4e2b-b5bc-d32a02705836" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1001a08a-7a6b-45f3-abda-16cb69f0a825" xlink:to="loc_us-gaap_ProductMember_c7174df2-3220-4e2b-b5bc-d32a02705836" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_QelbreeMember_ab564b48-e5c9-49d3-a1ae-c249f958dddc" xlink:href="supn-20240930.xsd#supn_QelbreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c7174df2-3220-4e2b-b5bc-d32a02705836" xlink:to="loc_supn_QelbreeMember_ab564b48-e5c9-49d3-a1ae-c249f958dddc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_GOCOVRIMember_1149bfe6-4dec-42c4-8b23-edcfa061aa78" xlink:href="supn-20240930.xsd#supn_GOCOVRIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c7174df2-3220-4e2b-b5bc-d32a02705836" xlink:to="loc_supn_GOCOVRIMember_1149bfe6-4dec-42c4-8b23-edcfa061aa78" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_OxtellarXRMember_3ade714d-3264-4e0c-9bca-12451a25f5dd" xlink:href="supn-20240930.xsd#supn_OxtellarXRMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c7174df2-3220-4e2b-b5bc-d32a02705836" xlink:to="loc_supn_OxtellarXRMember_3ade714d-3264-4e0c-9bca-12451a25f5dd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_APOKYNMember_47dea5dd-1fd6-4dd9-98c6-27db15518855" xlink:href="supn-20240930.xsd#supn_APOKYNMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c7174df2-3220-4e2b-b5bc-d32a02705836" xlink:to="loc_supn_APOKYNMember_47dea5dd-1fd6-4dd9-98c6-27db15518855" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_TrokendiXrMember_137a584b-78a5-424e-b3ef-fdd28c6c9dbd" xlink:href="supn-20240930.xsd#supn_TrokendiXrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c7174df2-3220-4e2b-b5bc-d32a02705836" xlink:to="loc_supn_TrokendiXrMember_137a584b-78a5-424e-b3ef-fdd28c6c9dbd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManufacturedProductOtherMember_a9d7f276-1a7c-4a85-8823-88cce3eac87b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ManufacturedProductOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c7174df2-3220-4e2b-b5bc-d32a02705836" xlink:to="loc_us-gaap_ManufacturedProductOtherMember_a9d7f276-1a7c-4a85-8823-88cce3eac87b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_RoyaltyLicenseAndOtherRevenueMember_98761a85-dc76-4287-940f-14f3226fbcc7" xlink:href="supn-20240930.xsd#supn_RoyaltyLicenseAndOtherRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1001a08a-7a6b-45f3-abda-16cb69f0a825" xlink:to="loc_supn_RoyaltyLicenseAndOtherRevenueMember_98761a85-dc76-4287-940f-14f3226fbcc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_36342b73-a228-44b2-9fcd-83dea4f1ea7b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_63937737-f6ed-46a4-b79e-b1a8329648f4" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_36342b73-a228-44b2-9fcd-83dea4f1ea7b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/FairValueofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#FairValueofFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/FairValueofFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_cd154e24-85dc-481a-a38a-79b666244a6e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_14593c4e-e558-4d9e-890e-f44b2b8ddc0e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_cd154e24-85dc-481a-a38a-79b666244a6e" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_14593c4e-e558-4d9e-890e-f44b2b8ddc0e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a294332c-e904-4834-8b8d-4357ad7cd86a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_14593c4e-e558-4d9e-890e-f44b2b8ddc0e" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a294332c-e904-4834-8b8d-4357ad7cd86a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_a294332c-e904-4834-8b8d-4357ad7cd86a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a294332c-e904-4834-8b8d-4357ad7cd86a" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_a294332c-e904-4834-8b8d-4357ad7cd86a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_0e4f4963-aa67-40f1-a6e5-8b18471fdbd8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a294332c-e904-4834-8b8d-4357ad7cd86a" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_0e4f4963-aa67-40f1-a6e5-8b18471fdbd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_d68420c4-a262-48cd-994a-c3ac3eee3b0e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_0e4f4963-aa67-40f1-a6e5-8b18471fdbd8" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_d68420c4-a262-48cd-994a-c3ac3eee3b0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_282223ca-4990-4c09-bf71-7c8eafe8f38e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_14593c4e-e558-4d9e-890e-f44b2b8ddc0e" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_282223ca-4990-4c09-bf71-7c8eafe8f38e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_282223ca-4990-4c09-bf71-7c8eafe8f38e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_282223ca-4990-4c09-bf71-7c8eafe8f38e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_282223ca-4990-4c09-bf71-7c8eafe8f38e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_103489d3-e473-4c4d-940e-4e0c36f8ef5e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_282223ca-4990-4c09-bf71-7c8eafe8f38e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_103489d3-e473-4c4d-940e-4e0c36f8ef5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_bc50a753-d5f1-429d-b4b7-15200aeabf3b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_103489d3-e473-4c4d-940e-4e0c36f8ef5e" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_bc50a753-d5f1-429d-b4b7-15200aeabf3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_88764516-aa2b-4c97-9660-0617b4e82459" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_103489d3-e473-4c4d-940e-4e0c36f8ef5e" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_88764516-aa2b-4c97-9660-0617b4e82459" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_c27fb46c-6137-45e5-a791-093c34490684" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_103489d3-e473-4c4d-940e-4e0c36f8ef5e" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_c27fb46c-6137-45e5-a791-093c34490684" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_1e41c60f-74a4-4c93-a589-360947f02989" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_14593c4e-e558-4d9e-890e-f44b2b8ddc0e" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_1e41c60f-74a4-4c93-a589-360947f02989" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_1e41c60f-74a4-4c93-a589-360947f02989_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_1e41c60f-74a4-4c93-a589-360947f02989" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_1e41c60f-74a4-4c93-a589-360947f02989_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_87819fa6-0d7e-4030-824c-bdc5ca5e71a7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_1e41c60f-74a4-4c93-a589-360947f02989" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_87819fa6-0d7e-4030-824c-bdc5ca5e71a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_b7e19f49-5bef-4710-baa3-5c5c342de383" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_87819fa6-0d7e-4030-824c-bdc5ca5e71a7" xlink:to="loc_us-gaap_CashMember_b7e19f49-5bef-4710-baa3-5c5c342de383" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_fe96468f-9fa8-4d75-aa55-740c6db8d37e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_87819fa6-0d7e-4030-824c-bdc5ca5e71a7" xlink:to="loc_us-gaap_MoneyMarketFundsMember_fe96468f-9fa8-4d75-aa55-740c6db8d37e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_995860b8-d767-4c6c-b571-cd0ce41a4e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_14593c4e-e558-4d9e-890e-f44b2b8ddc0e" xlink:to="loc_us-gaap_FinancialInstrumentAxis_995860b8-d767-4c6c-b571-cd0ce41a4e5b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_995860b8-d767-4c6c-b571-cd0ce41a4e5b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_995860b8-d767-4c6c-b571-cd0ce41a4e5b" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_995860b8-d767-4c6c-b571-cd0ce41a4e5b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fb1bd4f5-0946-4b02-9352-6ab1e95591c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_995860b8-d767-4c6c-b571-cd0ce41a4e5b" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fb1bd4f5-0946-4b02-9352-6ab1e95591c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CorporateAndUSGovernmentAgencyAndMunicipalDebtSecuritiesMember_ff7831fa-b188-41cd-9ee4-8082f685bedf" xlink:href="supn-20240930.xsd#supn_CorporateAndUSGovernmentAgencyAndMunicipalDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fb1bd4f5-0946-4b02-9352-6ab1e95591c6" xlink:to="loc_supn_CorporateAndUSGovernmentAgencyAndMunicipalDebtSecuritiesMember_ff7831fa-b188-41cd-9ee4-8082f685bedf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CorporateAndMunicipalDebtSecuritiesMember_b034c793-123d-48be-9e96-f1c517daa947" xlink:href="supn-20240930.xsd#supn_CorporateAndMunicipalDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fb1bd4f5-0946-4b02-9352-6ab1e95591c6" xlink:to="loc_supn_CorporateAndMunicipalDebtSecuritiesMember_b034c793-123d-48be-9e96-f1c517daa947" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_97b34a09-db3d-4fb9-b105-9fd6779fe789" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_cd154e24-85dc-481a-a38a-79b666244a6e" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_97b34a09-db3d-4fb9-b105-9fd6779fe789" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAbstract_820b2496-2c0c-4e84-aa19-abd94c3eeb43" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_97b34a09-db3d-4fb9-b105-9fd6779fe789" xlink:to="loc_us-gaap_CashAndCashEquivalentsAbstract_820b2496-2c0c-4e84-aa19-abd94c3eeb43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_42cf55e5-3b8c-432a-8542-33cd08ba6c66" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAbstract_820b2496-2c0c-4e84-aa19-abd94c3eeb43" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_42cf55e5-3b8c-432a-8542-33cd08ba6c66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesCurrentAbstract_7cd8ac55-07cf-4117-b312-bb56fe920596" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_97b34a09-db3d-4fb9-b105-9fd6779fe789" xlink:to="loc_us-gaap_DebtSecuritiesCurrentAbstract_7cd8ac55-07cf-4117-b312-bb56fe920596" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestCurrent_3c602216-4248-4613-ac6f-545aee0eb3f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesCurrentAbstract_7cd8ac55-07cf-4117-b312-bb56fe920596" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestCurrent_3c602216-4248-4613-ac6f-545aee0eb3f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_2c1ad32f-8f1e-4a0d-a395-bce5149a301c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_97b34a09-db3d-4fb9-b105-9fd6779fe789" xlink:to="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_2c1ad32f-8f1e-4a0d-a395-bce5149a301c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestNoncurrent_7e2ffc41-a8a9-465e-a62e-b44fe3bcdc7c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_2c1ad32f-8f1e-4a0d-a395-bce5149a301c" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestNoncurrent_7e2ffc41-a8a9-465e-a62e-b44fe3bcdc7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrentAbstract_fb89f956-c090-49c2-9970-7fc57a482e0b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherAssetsNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_97b34a09-db3d-4fb9-b105-9fd6779fe789" xlink:to="loc_us-gaap_OtherAssetsNoncurrentAbstract_fb89f956-c090-49c2-9970-7fc57a482e0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_3ee03459-17c7-4158-bf34-20ab135faeb4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsNoncurrentAbstract_fb89f956-c090-49c2-9970-7fc57a482e0b" xlink:to="loc_us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_3ee03459-17c7-4158-bf34-20ab135faeb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_a1de0b80-b752-421a-ab0a-defaf58502e4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_97b34a09-db3d-4fb9-b105-9fd6779fe789" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_a1de0b80-b752-421a-ab0a-defaf58502e4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_a0d8edfb-605d-4158-b601-f027b3ab3f0e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_cd154e24-85dc-481a-a38a-79b666244a6e" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_a0d8edfb-605d-4158-b601-f027b3ab3f0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_62e4f32c-b701-4725-8231-75ffbf390060" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_a0d8edfb-605d-4158-b601-f027b3ab3f0e" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_62e4f32c-b701-4725-8231-75ffbf390060" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_6a6a0ec3-c6a6-4c81-a51e-bcb4985603c2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_a0d8edfb-605d-4158-b601-f027b3ab3f0e" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_6a6a0ec3-c6a6-4c81-a51e-bcb4985603c2" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ContingentConsiderationNarrativeDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#ContingentConsiderationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ContingentConsiderationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c0f1ae9a-0f58-46e0-9aa5-d3d76953466c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c0f1ae9a-0f58-46e0-9aa5-d3d76953466c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5e006a27-7a2d-4381-8eac-1c259d8e3586" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c0f1ae9a-0f58-46e0-9aa5-d3d76953466c" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5e006a27-7a2d-4381-8eac-1c259d8e3586" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5e006a27-7a2d-4381-8eac-1c259d8e3586_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5e006a27-7a2d-4381-8eac-1c259d8e3586" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5e006a27-7a2d-4381-8eac-1c259d8e3586_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4452412d-5a78-4d7a-bddb-8b794aceb2f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5e006a27-7a2d-4381-8eac-1c259d8e3586" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4452412d-5a78-4d7a-bddb-8b794aceb2f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_417205ee-6f05-4a12-8576-7b8a70524438" xlink:href="supn-20240930.xsd#supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4452412d-5a78-4d7a-bddb-8b794aceb2f6" xlink:to="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_417205ee-6f05-4a12-8576-7b8a70524438" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_AdamasMember_f4e897ce-d435-424d-b589-cb675fd0b25b" xlink:href="supn-20240930.xsd#supn_AdamasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4452412d-5a78-4d7a-bddb-8b794aceb2f6" xlink:to="loc_supn_AdamasMember_f4e897ce-d435-424d-b589-cb675fd0b25b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_af434ce9-5f6c-41e8-83b2-2f48dc799118" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_c0f1ae9a-0f58-46e0-9aa5-d3d76953466c" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_af434ce9-5f6c-41e8-83b2-2f48dc799118" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_af434ce9-5f6c-41e8-83b2-2f48dc799118_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_af434ce9-5f6c-41e8-83b2-2f48dc799118" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_af434ce9-5f6c-41e8-83b2-2f48dc799118_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_b186d3d0-367a-4195-84e7-89f48a6bf3f8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_af434ce9-5f6c-41e8-83b2-2f48dc799118" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_b186d3d0-367a-4195-84e7-89f48a6bf3f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_SPN830NDAApprovalMilestoneMember_1fcbf8ff-dd0a-4c17-82d9-602294429671" xlink:href="supn-20240930.xsd#supn_SPN830NDAApprovalMilestoneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_b186d3d0-367a-4195-84e7-89f48a6bf3f8" xlink:to="loc_supn_SPN830NDAApprovalMilestoneMember_1fcbf8ff-dd0a-4c17-82d9-602294429671" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_SubsequentCommercialProductLaunchMember_5a2af7e1-62d0-4a30-911f-c72f779b14bd" xlink:href="supn-20240930.xsd#supn_SubsequentCommercialProductLaunchMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_b186d3d0-367a-4195-84e7-89f48a6bf3f8" xlink:to="loc_supn_SubsequentCommercialProductLaunchMember_5a2af7e1-62d0-4a30-911f-c72f779b14bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_Milestone2024AndMilestone2025Member_f0260a5f-0ab6-4ea7-a2ba-a0adc330669c" xlink:href="supn-20240930.xsd#supn_Milestone2024AndMilestone2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_b186d3d0-367a-4195-84e7-89f48a6bf3f8" xlink:to="loc_supn_Milestone2024AndMilestone2025Member_f0260a5f-0ab6-4ea7-a2ba-a0adc330669c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_Milestone2024Member_0ce1cc73-ea8a-415d-a273-523c6527f2ef" xlink:href="supn-20240930.xsd#supn_Milestone2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_Milestone2024AndMilestone2025Member_f0260a5f-0ab6-4ea7-a2ba-a0adc330669c" xlink:to="loc_supn_Milestone2024Member_0ce1cc73-ea8a-415d-a273-523c6527f2ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_cab77b73-0c0e-4ab5-8bd2-0168aafc7756" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_cab77b73-0c0e-4ab5-8bd2-0168aafc7756" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_BusinessCombinationContingentConsiderationNumberOfContingentValueRightsPerCommonShare_a4de0b88-8bf5-434f-9d56-342cbf83213f" xlink:href="supn-20240930.xsd#supn_BusinessCombinationContingentConsiderationNumberOfContingentValueRightsPerCommonShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:to="loc_supn_BusinessCombinationContingentConsiderationNumberOfContingentValueRightsPerCommonShare_a4de0b88-8bf5-434f-9d56-342cbf83213f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_BusinessCombinationContingentConsiderationArrangementsValuePricePerShare_8cf5d65a-ae28-4c73-bd5a-0057b22899ae" xlink:href="supn-20240930.xsd#supn_BusinessCombinationContingentConsiderationArrangementsValuePricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:to="loc_supn_BusinessCombinationContingentConsiderationArrangementsValuePricePerShare_8cf5d65a-ae28-4c73-bd5a-0057b22899ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValue_f264bdf3-a72b-4c50-a558-26f808ee89a2" xlink:href="supn-20240930.xsd#supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:to="loc_supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValue_f264bdf3-a72b-4c50-a558-26f808ee89a2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValueTerm_35684885-081d-4089-8386-11379e58a9ad" xlink:href="supn-20240930.xsd#supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValueTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:to="loc_supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValueTerm_35684885-081d-4089-8386-11379e58a9ad" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow_2f4ca4e5-9a04-432e-935f-179ede06ff07" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow_2f4ca4e5-9a04-432e-935f-179ede06ff07" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_8c7b0c5a-4e23-4954-bd20-543eee709c49" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_a71abfa2-6ae2-481a-9c04-4cec410c9790" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_8c7b0c5a-4e23-4954-bd20-543eee709c49" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ContingentConsiderationReconciliationoftheBeginningandEndingBalancesRelatedtotheContingentConsiderationDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#ContingentConsiderationReconciliationoftheBeginningandEndingBalancesRelatedtotheContingentConsiderationDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ContingentConsiderationReconciliationoftheBeginningandEndingBalancesRelatedtotheContingentConsiderationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c117b8c2-f4d5-4674-b9db-e684c5055475" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a9b657a1-3116-43a7-81bf-946715a7ea97" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c117b8c2-f4d5-4674-b9db-e684c5055475" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a9b657a1-3116-43a7-81bf-946715a7ea97" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_3059d429-1126-4ced-983c-97a3048a8303" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_a9b657a1-3116-43a7-81bf-946715a7ea97" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_3059d429-1126-4ced-983c-97a3048a8303" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3059d429-1126-4ced-983c-97a3048a8303_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_3059d429-1126-4ced-983c-97a3048a8303" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3059d429-1126-4ced-983c-97a3048a8303_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_80a520c2-7467-49d1-b5bb-526174752a3a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_3059d429-1126-4ced-983c-97a3048a8303" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_80a520c2-7467-49d1-b5bb-526174752a3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_483a8105-33a4-43dc-9a6e-f6eb3fe90957" xlink:href="supn-20240930.xsd#supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_80a520c2-7467-49d1-b5bb-526174752a3a" xlink:to="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_483a8105-33a4-43dc-9a6e-f6eb3fe90957" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_AdamasMember_76d9745d-7fad-48c5-a6f9-28e6f5a6e683" xlink:href="supn-20240930.xsd#supn_AdamasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_80a520c2-7467-49d1-b5bb-526174752a3a" xlink:to="loc_supn_AdamasMember_76d9745d-7fad-48c5-a6f9-28e6f5a6e683" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_8e7728b3-74f9-421a-b42d-0fbb26b983e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c117b8c2-f4d5-4674-b9db-e684c5055475" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_8e7728b3-74f9-421a-b42d-0fbb26b983e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_2960eda5-ee05-41c3-a89c-82492573f8cf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_8e7728b3-74f9-421a-b42d-0fbb26b983e2" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_2960eda5-ee05-41c3-a89c-82492573f8cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_e45370ea-67d7-4d56-bfd0-cbf7393076ff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_8e7728b3-74f9-421a-b42d-0fbb26b983e2" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_e45370ea-67d7-4d56-bfd0-cbf7393076ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_3a53106f-2f22-4ee2-8e51-8a458b847620" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/IntangibleAssetsNetIntangibleAssetsGrossCarryingAmountandRelatedAccumulatedAmortizationDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#IntangibleAssetsNetIntangibleAssetsGrossCarryingAmountandRelatedAccumulatedAmortizationDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/IntangibleAssetsNetIntangibleAssetsGrossCarryingAmountandRelatedAccumulatedAmortizationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_bb9b29b8-24a8-4608-b485-d16fe44a2531" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_50c098df-d054-4b84-98aa-54fa8da0c243" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_bb9b29b8-24a8-4608-b485-d16fe44a2531" xlink:to="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_50c098df-d054-4b84-98aa-54fa8da0c243" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_f9099c71-3b37-4caa-913b-785451ec86d5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_50c098df-d054-4b84-98aa-54fa8da0c243" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_f9099c71-3b37-4caa-913b-785451ec86d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_f9099c71-3b37-4caa-913b-785451ec86d5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_f9099c71-3b37-4caa-913b-785451ec86d5" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_f9099c71-3b37-4caa-913b-785451ec86d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_66049574-ec2c-4925-9516-3d5e16542e6a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_f9099c71-3b37-4caa-913b-785451ec86d5" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_66049574-ec2c-4925-9516-3d5e16542e6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_7439fe50-feb8-4899-9685-fa0ebf166572" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_66049574-ec2c-4925-9516-3d5e16542e6a" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_7439fe50-feb8-4899-9685-fa0ebf166572" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_de6fb7bf-7527-4e18-aa8d-e03e2aaa556c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_bb9b29b8-24a8-4608-b485-d16fe44a2531" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_de6fb7bf-7527-4e18-aa8d-e03e2aaa556c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_6c074f33-e162-4f5e-ad59-823ec1fc8430" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_0723c9a0-db48-4e66-836c-4dc98232d669" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_6c074f33-e162-4f5e-ad59-823ec1fc8430" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_0723c9a0-db48-4e66-836c-4dc98232d669" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_bc2aa840-8e7a-4ac4-a277-6717b9f29b8b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_0723c9a0-db48-4e66-836c-4dc98232d669" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_bc2aa840-8e7a-4ac4-a277-6717b9f29b8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_bc2aa840-8e7a-4ac4-a277-6717b9f29b8b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_bc2aa840-8e7a-4ac4-a277-6717b9f29b8b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_bc2aa840-8e7a-4ac4-a277-6717b9f29b8b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3ab7419e-c86f-4205-a5f4-bd7b2632d996" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_bc2aa840-8e7a-4ac4-a277-6717b9f29b8b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3ab7419e-c86f-4205-a5f4-bd7b2632d996" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_5899c5b1-0a11-49d6-988d-a0167cc1a164" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3ab7419e-c86f-4205-a5f4-bd7b2632d996" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_5899c5b1-0a11-49d6-988d-a0167cc1a164" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PatentDefenseCostsMember_bf1f8d6e-7ca2-42ca-bc2a-df85b9aec30f" xlink:href="supn-20240930.xsd#supn_PatentDefenseCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3ab7419e-c86f-4205-a5f4-bd7b2632d996" xlink:to="loc_supn_PatentDefenseCostsMember_bf1f8d6e-7ca2-42ca-bc2a-df85b9aec30f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_b05bef24-c0cb-476c-af04-d70de9a3b82b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_6c074f33-e162-4f5e-ad59-823ec1fc8430" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_b05bef24-c0cb-476c-af04-d70de9a3b82b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_d4159592-7af7-4edb-ae86-782fb3baef00" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_6c074f33-e162-4f5e-ad59-823ec1fc8430" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_d4159592-7af7-4edb-ae86-782fb3baef00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_f0e6eb33-48d1-4ff6-8eda-c2ad7398eadc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_6c074f33-e162-4f5e-ad59-823ec1fc8430" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_f0e6eb33-48d1-4ff6-8eda-c2ad7398eadc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_ba189d90-f939-4176-904b-06da4540376b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_6c074f33-e162-4f5e-ad59-823ec1fc8430" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_ba189d90-f939-4176-904b-06da4540376b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/DebtDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#DebtDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/DebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_a81393a6-228d-454d-ac4e-b9e2f93e7d69" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_50a0f188-4c62-49b1-8fc9-f73675e3b968" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a81393a6-228d-454d-ac4e-b9e2f93e7d69" xlink:to="loc_us-gaap_DebtInstrumentTable_50a0f188-4c62-49b1-8fc9-f73675e3b968" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_12c41be0-bec2-4b9f-a092-723d6d7c233d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_50a0f188-4c62-49b1-8fc9-f73675e3b968" xlink:to="loc_us-gaap_CreditFacilityAxis_12c41be0-bec2-4b9f-a092-723d6d7c233d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_12c41be0-bec2-4b9f-a092-723d6d7c233d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_12c41be0-bec2-4b9f-a092-723d6d7c233d" xlink:to="loc_us-gaap_CreditFacilityDomain_12c41be0-bec2-4b9f-a092-723d6d7c233d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_57df8809-f931-441d-ad45-f83aa11c79fb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_12c41be0-bec2-4b9f-a092-723d6d7c233d" xlink:to="loc_us-gaap_CreditFacilityDomain_57df8809-f931-441d-ad45-f83aa11c79fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_UncommittedSecuredCreditLineMember_e68f5c4b-3e95-4e3d-b608-db4e5eed2e8b" xlink:href="supn-20240930.xsd#supn_UncommittedSecuredCreditLineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_57df8809-f931-441d-ad45-f83aa11c79fb" xlink:to="loc_supn_UncommittedSecuredCreditLineMember_e68f5c4b-3e95-4e3d-b608-db4e5eed2e8b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_856a1895-7704-48a2-875a-37d0c217646d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_57df8809-f931-441d-ad45-f83aa11c79fb" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_856a1895-7704-48a2-875a-37d0c217646d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_f36894b0-1fa0-42e7-9dc4-4d2d0572629c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_50a0f188-4c62-49b1-8fc9-f73675e3b968" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_f36894b0-1fa0-42e7-9dc4-4d2d0572629c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_f36894b0-1fa0-42e7-9dc4-4d2d0572629c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_f36894b0-1fa0-42e7-9dc4-4d2d0572629c" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_f36894b0-1fa0-42e7-9dc4-4d2d0572629c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_183d35b3-ceb6-475a-88ae-e01021e6f3ef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_f36894b0-1fa0-42e7-9dc4-4d2d0572629c" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_183d35b3-ceb6-475a-88ae-e01021e6f3ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_3fcb5a9c-75da-4c33-a120-f31dbb591aed" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_183d35b3-ceb6-475a-88ae-e01021e6f3ef" xlink:to="loc_us-gaap_LineOfCreditMember_3fcb5a9c-75da-4c33-a120-f31dbb591aed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_f5df8688-8789-4e9f-b01f-a29d55ecd49e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_183d35b3-ceb6-475a-88ae-e01021e6f3ef" xlink:to="loc_us-gaap_ConvertibleDebtMember_f5df8688-8789-4e9f-b01f-a29d55ecd49e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_fea4ba00-6a79-47d5-a444-981b129649cd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a81393a6-228d-454d-ac4e-b9e2f93e7d69" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_fea4ba00-6a79-47d5-a444-981b129649cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_55195e7a-ef1e-4cfb-9ad9-a9dc9aaa8ebd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a81393a6-228d-454d-ac4e-b9e2f93e7d69" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_55195e7a-ef1e-4cfb-9ad9-a9dc9aaa8ebd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_303ba196-7ed8-4b93-ba65-1d076d13bf6b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a81393a6-228d-454d-ac4e-b9e2f93e7d69" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_303ba196-7ed8-4b93-ba65-1d076d13bf6b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_8e228eb2-d477-4814-baed-61febfb0ad37" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a81393a6-228d-454d-ac4e-b9e2f93e7d69" xlink:to="loc_us-gaap_InterestExpenseDebt_8e228eb2-d477-4814-baed-61febfb0ad37" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_c6fbd9f5-06c7-4fe4-ab01-e075c23f3ce1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a81393a6-228d-454d-ac4e-b9e2f93e7d69" xlink:to="loc_us-gaap_ShortTermBorrowings_c6fbd9f5-06c7-4fe4-ab01-e075c23f3ce1" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsNarrativesDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#ShareBasedPaymentsNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsNarrativesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_47d6da9a-0a3d-4f0a-8e90-ec077584f79a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a1437d1c-b2f3-4a33-9344-1c4c22d8a7ac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_47d6da9a-0a3d-4f0a-8e90-ec077584f79a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a1437d1c-b2f3-4a33-9344-1c4c22d8a7ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_9798cdcb-8913-4da7-847a-e5c734487392" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a1437d1c-b2f3-4a33-9344-1c4c22d8a7ac" xlink:to="loc_us-gaap_PlanNameAxis_9798cdcb-8913-4da7-847a-e5c734487392" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_9798cdcb-8913-4da7-847a-e5c734487392_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_9798cdcb-8913-4da7-847a-e5c734487392" xlink:to="loc_us-gaap_PlanNameDomain_9798cdcb-8913-4da7-847a-e5c734487392_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_3ea8ba50-0005-4cc0-9fcd-5b9f4d81dbc7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_9798cdcb-8913-4da7-847a-e5c734487392" xlink:to="loc_us-gaap_PlanNameDomain_3ea8ba50-0005-4cc0-9fcd-5b9f4d81dbc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_A2021EquityIncentivePlanMember_8b7b659d-567b-4101-853a-030afdd7a207" xlink:href="supn-20240930.xsd#supn_A2021EquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_3ea8ba50-0005-4cc0-9fcd-5b9f4d81dbc7" xlink:to="loc_supn_A2021EquityIncentivePlanMember_8b7b659d-567b-4101-853a-030afdd7a207" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_8069487c-c0d0-4dad-bb60-3373fd491421" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_47d6da9a-0a3d-4f0a-8e90-ec077584f79a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_8069487c-c0d0-4dad-bb60-3373fd491421" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsSharebasedCompensationExpenseDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#ShareBasedPaymentsSharebasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsSharebasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_25beeea9-1185-424f-80a1-12bbe3309d55" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_8a5a7c3a-3b18-4ab1-812c-b40ffda61206" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_25beeea9-1185-424f-80a1-12bbe3309d55" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_8a5a7c3a-3b18-4ab1-812c-b40ffda61206" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_03ec2326-e53f-40a3-bf27-215cbf757993" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_8a5a7c3a-3b18-4ab1-812c-b40ffda61206" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_03ec2326-e53f-40a3-bf27-215cbf757993" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_03ec2326-e53f-40a3-bf27-215cbf757993_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_03ec2326-e53f-40a3-bf27-215cbf757993" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_03ec2326-e53f-40a3-bf27-215cbf757993_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_fc23202a-998e-407c-b6c4-5393b0909b01" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_03ec2326-e53f-40a3-bf27-215cbf757993" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_fc23202a-998e-407c-b6c4-5393b0909b01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_330b8983-7f88-4f7e-ae50-324f914cd7fe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fc23202a-998e-407c-b6c4-5393b0909b01" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_330b8983-7f88-4f7e-ae50-324f914cd7fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_6d28c3a2-29c5-4c92-ae30-9657a038b773" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fc23202a-998e-407c-b6c4-5393b0909b01" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_6d28c3a2-29c5-4c92-ae30-9657a038b773" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_f52fe7fb-7ec1-40d9-9552-33e1b8eb6761" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_25beeea9-1185-424f-80a1-12bbe3309d55" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_f52fe7fb-7ec1-40d9-9552-33e1b8eb6761" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsRestrictedStockUnitsDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#ShareBasedPaymentsRestrictedStockUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsRestrictedStockUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_af8969c8-681f-4f39-87bf-5e5b9b33cd80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1d55dc35-61d9-4657-ad22-37adf8e12d01" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_af8969c8-681f-4f39-87bf-5e5b9b33cd80" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1d55dc35-61d9-4657-ad22-37adf8e12d01" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_0f5187d4-73f5-47af-8be5-68458402dbfa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1d55dc35-61d9-4657-ad22-37adf8e12d01" xlink:to="loc_us-gaap_AwardTypeAxis_0f5187d4-73f5-47af-8be5-68458402dbfa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0f5187d4-73f5-47af-8be5-68458402dbfa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_0f5187d4-73f5-47af-8be5-68458402dbfa" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0f5187d4-73f5-47af-8be5-68458402dbfa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_bd8ffa96-a4f4-41a7-b115-fc847b65b156" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_0f5187d4-73f5-47af-8be5-68458402dbfa" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_bd8ffa96-a4f4-41a7-b115-fc847b65b156" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_07a5a27a-01d7-4ca0-ae81-939dc9b39860" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_bd8ffa96-a4f4-41a7-b115-fc847b65b156" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_07a5a27a-01d7-4ca0-ae81-939dc9b39860" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_53418315-700c-4395-9e4b-2097e7bdca3e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_af8969c8-681f-4f39-87bf-5e5b9b33cd80" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_53418315-700c-4395-9e4b-2097e7bdca3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_ae2d295a-56a3-4e6a-ab67-024183896c4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_53418315-700c-4395-9e4b-2097e7bdca3e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_ae2d295a-56a3-4e6a-ab67-024183896c4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_d461e527-b9fd-499d-acd7-3af2d851aa2f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_53418315-700c-4395-9e4b-2097e7bdca3e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_d461e527-b9fd-499d-acd7-3af2d851aa2f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_289096e8-5eab-4a2b-ba7d-4a4c7350c209" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_53418315-700c-4395-9e4b-2097e7bdca3e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_289096e8-5eab-4a2b-ba7d-4a4c7350c209" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_938748e0-eaa9-4543-b200-d6722c04c27f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_53418315-700c-4395-9e4b-2097e7bdca3e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_938748e0-eaa9-4543-b200-d6722c04c27f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_2955af03-796f-45c8-92f4-f62d2b971e16" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e32b839c-a7ed-4339-8a35-6e99d4ddee8d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_af8969c8-681f-4f39-87bf-5e5b9b33cd80" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e32b839c-a7ed-4339-8a35-6e99d4ddee8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_4822d968-099f-4263-8235-c5d7792a3aa1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e32b839c-a7ed-4339-8a35-6e99d4ddee8d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_4822d968-099f-4263-8235-c5d7792a3aa1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_8d309eef-1a89-4303-a3dd-d423c684435d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e32b839c-a7ed-4339-8a35-6e99d4ddee8d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_8d309eef-1a89-4303-a3dd-d423c684435d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_1eb6ceb6-7f46-49de-9744-82852f2bdd00" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e32b839c-a7ed-4339-8a35-6e99d4ddee8d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_1eb6ceb6-7f46-49de-9744-82852f2bdd00" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_479d8f0b-ff11-4284-961f-b89886da7b41" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e32b839c-a7ed-4339-8a35-6e99d4ddee8d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_479d8f0b-ff11-4284-961f-b89886da7b41" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_c3311243-6fd4-467f-8887-cb56a74efddd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsPerformanceStockUnitsDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#ShareBasedPaymentsPerformanceStockUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsPerformanceStockUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50c1f18e-ed43-4a1d-95aa-3d774ad90c6c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4e2b1c0e-2d51-4d68-a452-98bdc5c36d98" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50c1f18e-ed43-4a1d-95aa-3d774ad90c6c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4e2b1c0e-2d51-4d68-a452-98bdc5c36d98" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_9ec76b7f-677c-4169-b4f1-96ad36766dd9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4e2b1c0e-2d51-4d68-a452-98bdc5c36d98" xlink:to="loc_us-gaap_AwardTypeAxis_9ec76b7f-677c-4169-b4f1-96ad36766dd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9ec76b7f-677c-4169-b4f1-96ad36766dd9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_9ec76b7f-677c-4169-b4f1-96ad36766dd9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9ec76b7f-677c-4169-b4f1-96ad36766dd9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_987d4e44-852d-4e52-a348-5fe0ef8caee1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_9ec76b7f-677c-4169-b4f1-96ad36766dd9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_987d4e44-852d-4e52-a348-5fe0ef8caee1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_784cfea6-e7b0-4543-af7e-5034fb64a0cf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_987d4e44-852d-4e52-a348-5fe0ef8caee1" xlink:to="loc_us-gaap_PerformanceSharesMember_784cfea6-e7b0-4543-af7e-5034fb64a0cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PerformanceBasedUnitsMember_daadc913-140d-4c51-8d99-d27007d67db4" xlink:href="supn-20240930.xsd#supn_PerformanceBasedUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PerformanceSharesMember_784cfea6-e7b0-4543-af7e-5034fb64a0cf" xlink:to="loc_supn_PerformanceBasedUnitsMember_daadc913-140d-4c51-8d99-d27007d67db4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MarketBasedUnitsMember_012ca17a-329a-43d8-ae81-c1eb06d04bab" xlink:href="supn-20240930.xsd#supn_MarketBasedUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PerformanceSharesMember_784cfea6-e7b0-4543-af7e-5034fb64a0cf" xlink:to="loc_supn_MarketBasedUnitsMember_012ca17a-329a-43d8-ae81-c1eb06d04bab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_89fcac52-a443-4f75-90d0-37f31a4bbd42" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50c1f18e-ed43-4a1d-95aa-3d774ad90c6c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_89fcac52-a443-4f75-90d0-37f31a4bbd42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_d81b4c5a-b332-4a12-a2f6-3e78f4ca605d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_89fcac52-a443-4f75-90d0-37f31a4bbd42" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_d81b4c5a-b332-4a12-a2f6-3e78f4ca605d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_833f6d45-e7c0-4eb6-adf6-a8faea90e54d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_89fcac52-a443-4f75-90d0-37f31a4bbd42" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_833f6d45-e7c0-4eb6-adf6-a8faea90e54d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_faaa2bd4-7584-4716-a266-9e49c5fbe3d4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_89fcac52-a443-4f75-90d0-37f31a4bbd42" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_faaa2bd4-7584-4716-a266-9e49c5fbe3d4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_93d25676-c886-4cc8-b2b2-3ccbf3715eb4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_89fcac52-a443-4f75-90d0-37f31a4bbd42" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_93d25676-c886-4cc8-b2b2-3ccbf3715eb4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_694193a7-2e62-4842-bb68-1ab8a535dc37" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_8012547c-6fb7-46b9-8c77-24ad970defb4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50c1f18e-ed43-4a1d-95aa-3d774ad90c6c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_8012547c-6fb7-46b9-8c77-24ad970defb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_551e462b-ad79-4515-9564-1ded1e55d647" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_8012547c-6fb7-46b9-8c77-24ad970defb4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_551e462b-ad79-4515-9564-1ded1e55d647" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_10593d4e-745b-435f-97ab-a29d45d5efe7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_8012547c-6fb7-46b9-8c77-24ad970defb4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_10593d4e-745b-435f-97ab-a29d45d5efe7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_e2101293-4259-4467-976a-58024ce13d82" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_8012547c-6fb7-46b9-8c77-24ad970defb4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_e2101293-4259-4467-976a-58024ce13d82" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_736d108c-9ba3-42ff-a785-d0248372e121" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_8012547c-6fb7-46b9-8c77-24ad970defb4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_736d108c-9ba3-42ff-a785-d0248372e121" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_68e046f2-ec79-4e38-a462-5e42240de333" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/EarningsLossperShareScheduleofCommonStockEquivalentsExcludedintheCalculationofDilutedEarningsperShareDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#EarningsLossperShareScheduleofCommonStockEquivalentsExcludedintheCalculationofDilutedEarningsperShareDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/EarningsLossperShareScheduleofCommonStockEquivalentsExcludedintheCalculationofDilutedEarningsperShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_a7b85bb6-367a-413a-811d-842cf8b4bdb7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_8dd2a788-861e-445d-85c9-a313d3ec31f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_a7b85bb6-367a-413a-811d-842cf8b4bdb7" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_8dd2a788-861e-445d-85c9-a313d3ec31f6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1b636aa1-269c-4e70-b99a-ee60fa704d24" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_8dd2a788-861e-445d-85c9-a313d3ec31f6" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1b636aa1-269c-4e70-b99a-ee60fa704d24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_1b636aa1-269c-4e70-b99a-ee60fa704d24_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1b636aa1-269c-4e70-b99a-ee60fa704d24" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_1b636aa1-269c-4e70-b99a-ee60fa704d24_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_70da5f05-7be4-4f25-86b3-1a116d984ca1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1b636aa1-269c-4e70-b99a-ee60fa704d24" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_70da5f05-7be4-4f25-86b3-1a116d984ca1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_2fc72e24-7e87-4d9c-b300-e07937cdc1db" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_70da5f05-7be4-4f25-86b3-1a116d984ca1" xlink:to="loc_us-gaap_ConvertibleDebtMember_2fc72e24-7e87-4d9c-b300-e07937cdc1db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_a24f6548-a8d4-4482-8344-9f97994df9d6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_70da5f05-7be4-4f25-86b3-1a116d984ca1" xlink:to="loc_us-gaap_StockCompensationPlanMember_a24f6548-a8d4-4482-8344-9f97994df9d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_6134eaa9-3785-4212-b738-8d5299587447" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_a7b85bb6-367a-413a-811d-842cf8b4bdb7" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_6134eaa9-3785-4212-b738-8d5299587447" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/CompositionofOtherBalanceSheetItemsPropertyandEquipmentDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#CompositionofOtherBalanceSheetItemsPropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/CompositionofOtherBalanceSheetItemsPropertyandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2abc20e-1228-46d0-8bed-60a9bf9c6635" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_2d3b19b4-1f20-435c-80de-5e5392d5e49d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2abc20e-1228-46d0-8bed-60a9bf9c6635" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_2d3b19b4-1f20-435c-80de-5e5392d5e49d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_62e73583-1520-4431-bce2-8937a3791175" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_2d3b19b4-1f20-435c-80de-5e5392d5e49d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_62e73583-1520-4431-bce2-8937a3791175" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_62e73583-1520-4431-bce2-8937a3791175_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_62e73583-1520-4431-bce2-8937a3791175" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_62e73583-1520-4431-bce2-8937a3791175_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_14807d36-01f6-4194-972d-26b89b67a9ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_62e73583-1520-4431-bce2-8937a3791175" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_14807d36-01f6-4194-972d-26b89b67a9ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_LabEquipmentAndFurnitureMember_8adef13b-4c46-4903-a456-a4ed7a7cd6d7" xlink:href="supn-20240930.xsd#supn_LabEquipmentAndFurnitureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_14807d36-01f6-4194-972d-26b89b67a9ae" xlink:to="loc_supn_LabEquipmentAndFurnitureMember_8adef13b-4c46-4903-a456-a4ed7a7cd6d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_3020368e-ef8a-46fa-bd63-9a95ffd50641" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_14807d36-01f6-4194-972d-26b89b67a9ae" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_3020368e-ef8a-46fa-bd63-9a95ffd50641" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_2da2002b-0993-4641-9f4b-4e56c6e1b4cf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_14807d36-01f6-4194-972d-26b89b67a9ae" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_2da2002b-0993-4641-9f4b-4e56c6e1b4cf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_5cc4e413-7166-4694-ab35-c6a5e6385304" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_14807d36-01f6-4194-972d-26b89b67a9ae" xlink:to="loc_us-gaap_ComputerEquipmentMember_5cc4e413-7166-4694-ab35-c6a5e6385304" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_e84bfa62-4efd-4701-aaa4-47f1e6d03595" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2abc20e-1228-46d0-8bed-60a9bf9c6635" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_e84bfa62-4efd-4701-aaa4-47f1e6d03595" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_30f687e4-586b-4222-a7cc-f9a9b1b9e8f8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2abc20e-1228-46d0-8bed-60a9bf9c6635" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_30f687e4-586b-4222-a7cc-f9a9b1b9e8f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_ad7db635-0174-44d3-b2cc-b762f1d85f6a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2abc20e-1228-46d0-8bed-60a9bf9c6635" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_ad7db635-0174-44d3-b2cc-b762f1d85f6a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_82c4e2a0-f8c4-4378-b31d-0e90a2951d78" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2abc20e-1228-46d0-8bed-60a9bf9c6635" xlink:to="loc_us-gaap_DepreciationAndAmortization_82c4e2a0-f8c4-4378-b31d-0e90a2951d78" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="supn-20240930.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/CommitmentsandContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermPurchaseCommitmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentTable_92932116-c26b-44ae-b1cb-4e6b3c7c5abd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermPurchaseCommitmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentTable_92932116-c26b-44ae-b1cb-4e6b3c7c5abd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5f53773b-0d42-4af6-9762-553d07c4b503" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_92932116-c26b-44ae-b1cb-4e6b3c7c5abd" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5f53773b-0d42-4af6-9762-553d07c4b503" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5f53773b-0d42-4af6-9762-553d07c4b503_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5f53773b-0d42-4af6-9762-553d07c4b503" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5f53773b-0d42-4af6-9762-553d07c4b503_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cd2371bd-c888-4132-b010-81b1ba42fa64" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5f53773b-0d42-4af6-9762-553d07c4b503" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cd2371bd-c888-4132-b010-81b1ba42fa64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_279733ad-0a25-4971-aeb3-403075ea4797" xlink:href="supn-20240930.xsd#supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cd2371bd-c888-4132-b010-81b1ba42fa64" xlink:to="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_279733ad-0a25-4971-aeb3-403075ea4797" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_f090b8eb-befd-4e0a-a19f-a09a65992f2b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_92932116-c26b-44ae-b1cb-4e6b3c7c5abd" xlink:to="loc_srt_LitigationCaseAxis_f090b8eb-befd-4e0a-a19f-a09a65992f2b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_f090b8eb-befd-4e0a-a19f-a09a65992f2b_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_f090b8eb-befd-4e0a-a19f-a09a65992f2b" xlink:to="loc_srt_LitigationCaseTypeDomain_f090b8eb-befd-4e0a-a19f-a09a65992f2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_be2ae165-fdbd-40d0-8388-3161618eebde" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_f090b8eb-befd-4e0a-a19f-a09a65992f2b" xlink:to="loc_srt_LitigationCaseTypeDomain_be2ae165-fdbd-40d0-8388-3161618eebde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_NAMENDAXRNamzaricQuiTamLitigationMember_de82e4dd-a620-4aa9-846e-6150353f7521" xlink:href="supn-20240930.xsd#supn_NAMENDAXRNamzaricQuiTamLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_be2ae165-fdbd-40d0-8388-3161618eebde" xlink:to="loc_supn_NAMENDAXRNamzaricQuiTamLitigationMember_de82e4dd-a620-4aa9-846e-6150353f7521" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_7cb8fa8e-1a31-42fe-b446-84b2e4611d3f" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_92932116-c26b-44ae-b1cb-4e6b3c7c5abd" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_7cb8fa8e-1a31-42fe-b446-84b2e4611d3f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_7cb8fa8e-1a31-42fe-b446-84b2e4611d3f_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_7cb8fa8e-1a31-42fe-b446-84b2e4611d3f" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_7cb8fa8e-1a31-42fe-b446-84b2e4611d3f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_e57114b6-3837-4f84-910e-85158c39777a" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_7cb8fa8e-1a31-42fe-b446-84b2e4611d3f" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_e57114b6-3837-4f84-910e-85158c39777a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_NavitorPharmaceuticalsIncMember_208a7918-3d97-4dab-9275-4a144a728c6c" xlink:href="supn-20240930.xsd#supn_NavitorPharmaceuticalsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_e57114b6-3837-4f84-910e-85158c39777a" xlink:to="loc_supn_NavitorPharmaceuticalsIncMember_208a7918-3d97-4dab-9275-4a144a728c6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_a923da54-e26d-4786-9a8a-479585f1dc3c" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_92932116-c26b-44ae-b1cb-4e6b3c7c5abd" xlink:to="loc_srt_ConsolidatedEntitiesAxis_a923da54-e26d-4786-9a8a-479585f1dc3c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_a923da54-e26d-4786-9a8a-479585f1dc3c_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_a923da54-e26d-4786-9a8a-479585f1dc3c" xlink:to="loc_srt_ConsolidatedEntitiesDomain_a923da54-e26d-4786-9a8a-479585f1dc3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_fb4cc7b8-4637-4318-8462-c6191e7a91a3" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_a923da54-e26d-4786-9a8a-479585f1dc3c" xlink:to="loc_srt_ConsolidatedEntitiesDomain_fb4cc7b8-4637-4318-8462-c6191e7a91a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_4e364975-ebed-4f15-ae78-1d3d79460636" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_fb4cc7b8-4637-4318-8462-c6191e7a91a3" xlink:to="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_4e364975-ebed-4f15-ae78-1d3d79460636" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_80d5e04d-83e5-4c9b-ab61-785c781c0884" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_92932116-c26b-44ae-b1cb-4e6b3c7c5abd" xlink:to="loc_srt_RangeAxis_80d5e04d-83e5-4c9b-ab61-785c781c0884" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_80d5e04d-83e5-4c9b-ab61-785c781c0884_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_80d5e04d-83e5-4c9b-ab61-785c781c0884" xlink:to="loc_srt_RangeMember_80d5e04d-83e5-4c9b-ab61-785c781c0884_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d7ea120e-26b4-4d9d-979c-1a24ca75ab57" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_80d5e04d-83e5-4c9b-ab61-785c781c0884" xlink:to="loc_srt_RangeMember_d7ea120e-26b4-4d9d-979c-1a24ca75ab57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_15efdcdd-939c-4181-a8ef-c8e0727b322d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_d7ea120e-26b4-4d9d-979c-1a24ca75ab57" xlink:to="loc_srt_MinimumMember_15efdcdd-939c-4181-a8ef-c8e0727b322d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_e7a18467-6cfb-4e62-aa68-6719daadf417" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_d7ea120e-26b4-4d9d-979c-1a24ca75ab57" xlink:to="loc_srt_MaximumMember_e7a18467-6cfb-4e62-aa68-6719daadf417" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementAgreementTerminationNoticePeriod_d8ca5301-966a-41c8-9851-343c95fb912a" xlink:href="supn-20240930.xsd#supn_CollaborativeArrangementAgreementTerminationNoticePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_supn_CollaborativeArrangementAgreementTerminationNoticePeriod_d8ca5301-966a-41c8-9851-343c95fb912a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementThresholdForDevelopmentCostsPayments_46e1edca-aae0-4067-a616-aa69ceec81ff" xlink:href="supn-20240930.xsd#supn_CollaborativeArrangementThresholdForDevelopmentCostsPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_supn_CollaborativeArrangementThresholdForDevelopmentCostsPayments_46e1edca-aae0-4067-a616-aa69ceec81ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementPaymentForOneTimeFee_aa65bb37-785a-435f-9095-2961ddf5388f" xlink:href="supn-20240930.xsd#supn_CollaborativeArrangementPaymentForOneTimeFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_supn_CollaborativeArrangementPaymentForOneTimeFee_aa65bb37-785a-435f-9095-2961ddf5388f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCost_31286edf-28ea-4cf6-9a15-804fbe5b852c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquitySecuritiesFvNiCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCost_31286edf-28ea-4cf6-9a15-804fbe5b852c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityOwnershipPercentage_1a6d2e3c-b9da-4043-acc0-e5724563281d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableInterestEntityOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_us-gaap_VariableInterestEntityOwnershipPercentage_1a6d2e3c-b9da-4043-acc0-e5724563281d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementExpectedDevelopmentCosts_9ab49631-5653-4f58-889c-e3389f0fea22" xlink:href="supn-20240930.xsd#supn_CollaborativeArrangementExpectedDevelopmentCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_supn_CollaborativeArrangementExpectedDevelopmentCosts_9ab49631-5653-4f58-889c-e3389f0fea22" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementUpfrontDevelopmentCosts_8220f984-151c-4712-9af5-25c0f7ab2ba5" xlink:href="supn-20240930.xsd#supn_CollaborativeArrangementUpfrontDevelopmentCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_supn_CollaborativeArrangementUpfrontDevelopmentCosts_8220f984-151c-4712-9af5-25c0f7ab2ba5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PurchaseCommitmentAnnualMinimumAmountCommitted_3edd6403-9ace-4bc6-9ad6-da2dd68c38b5" xlink:href="supn-20240930.xsd#supn_PurchaseCommitmentAnnualMinimumAmountCommitted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_supn_PurchaseCommitmentAnnualMinimumAmountCommitted_3edd6403-9ace-4bc6-9ad6-da2dd68c38b5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_e01e22bb-6c31-43ff-9407-c136036e47a3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_e01e22bb-6c31-43ff-9407-c136036e47a3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyDamagesSoughtValue_f687d16e-8485-4e20-b1f9-45896a376c93" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyDamagesSoughtValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_d6bbcf96-9048-4ef6-b585-49eb2c362de5" xlink:to="loc_us-gaap_LossContingencyDamagesSoughtValue_f687d16e-8485-4e20-b1f9-45896a376c93" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PerformanceBasedUnitsMember_6491e8fb-6d63-4d79-a50d-d3282394d1b7" xlink:href="supn-20240930.xsd#supn_PerformanceBasedUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_supn_PerformanceBasedUnitsMember_6491e8fb-6d63-4d79-a50d-d3282394d1b7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MarketBasedUnitsMember_0afe6fb3-bcb4-4142-b62a-c931a9d91519" xlink:href="supn-20240930.xsd#supn_MarketBasedUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_supn_MarketBasedUnitsMember_0afe6fb3-bcb4-4142-b62a-c931a9d91519" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_PerformanceSharesMember" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_JackKhattarMember_63e8a066-6459-4381-ab92-1ed46c13f2c7" xlink:href="supn-20240930.xsd#supn_JackKhattarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_supn_JackKhattarMember_63e8a066-6459-4381-ab92-1ed46c13f2c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PadmanabhBhattMember_8835539b-5319-4207-9326-395786f2d27f" xlink:href="supn-20240930.xsd#supn_PadmanabhBhattMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_supn_PadmanabhBhattMember_8835539b-5319-4207-9326-395786f2d27f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-roles-2024.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_OtherAssetsNoncurrent" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
