Project Kansas Commitment Letter

Exhibit 10.1

EXECUTION VERSION

April 10, 2011

Project Kansas

Commitment Letter

Endo Pharmaceuticals Holdings Inc.

100 Endo Boulevard

Chadds Ford, Pennsylvania 19317

Attention: Alan Levin, CFO

Ladies and Gentlemen:

You (the “Borrower”) have advised Morgan Stanley Senior Funding, Inc. (“MSSF”) and Merrill Lynch, Pierce, Fenner & Smith Incorporated (“MLPFS” and, collectively with MSSF, the “Lead Arrangers”) and Bank of America, N.A. (“BANA” and, collectively with MSSF, the “Commitment Parties”; together with the Lead Arrangers, “we” or “us”) that you intend to acquire the Target and consummate the other transactions described in the introductory paragraphs of the Summary of Terms and Conditions in respect of the Senior Secured Facilities attached as Exhibit A hereto (the “Senior Term Sheet” and, collectively with the Summary of Terms and Conditions in respect of the Bridge Facility attached as Exhibit B hereto (the “Bridge Term Sheet”), the “Term Sheet”). Capitalized terms used but not defined herein are used with the meanings assigned to them in the applicable Term Sheet.

In connection with the foregoing, you have requested that MSSF and MLPFS agree to (i) structure, arrange and syndicate a bridge loan facility to the Borrower in an aggregate principal amount of $700,000,000 (the “Bridge Facility”), (ii) arrange a senior secured term loan “A” facility in an aggregate principal amount of $1,500,000,000 (the “Term Loan A Facility”), (iii) arrange a senior secured term loan “B” facility in an aggregate principal amount of $900,000,000 (the “Term Loan B Facility” and, together with the Term Loan A Facility, the “Term Loan Facilities”) and (iv) arrange a multicurrency revolving credit facility in an initial aggregate principal amount of $500,000,000 (the “Revolving Credit Facility”, and together with the Term Loan Facilities, the “Senior Secured Facilities” and, together with the Bridge Facility, the “Facilities” and each such facility individually, a “Facility”). You have also requested that (w) MSSF commit to provide fifty percent (50%) of each of the Facilities on the Closing Date (as hereinafter defined), (x) BANA commit to provide fifty percent (50%) of each of the Facilities on the Closing Date, (y) MSSF agree to serve as administrative agent for the Facilities (other than the Bridge Facility) and as syndication agent for the Bridge Facility and (z) BANA agree to serve as administrative agent for the Bridge Facility and syndication agent for the Facilities (other than the Bridge Facility).

The Lead Arrangers are pleased to advise you that they are willing to act as joint lead arrangers and joint bookrunners for the Facilities. Furthermore, in connection with the foregoing, (i) MSSF is pleased to advise you of its several (but not joint) commitment to provide 50% of the aggregate principal amount of the Senior Secured Facilities on the Closing Date, and, in the event that the Borrower does not issue the full amount of the Senior Notes or other Securities (as defined in the Fee Letter) at or prior to the time the Acquisition is consummated, 50% of the aggregate principal amount of the Bridge Facility on the Closing Date and (ii) BANA is pleased to advise you of its several (but not joint) commitment to provide 50% of the aggregate principal amount of the Senior Secured Facilities on the Closing Date, and,

in the event that the Borrower does not issue the full amount of the Senior Notes or other Securities at or prior to the time the Acquisition is consummated, 50% of the aggregate principal amount of the Bridge Facility on the Closing Date, in each case upon the terms and subject to the conditions set forth in this commitment letter and in the Term Sheet (together with this commitment letter, the “Commitment Letter”).

It is agreed that MSSF will act as the sole and exclusive administrative agent (the “Administrative Agent”) for the Facilities (other than the Bridge Facility) and as sole and exclusive syndication agent for the Bridge Facility, that BANA will act as the sole and exclusive administrative agent for the Bridge Facility and as sole and exclusive syndication agent for the Facilities (other than the Bridge Facility) and that the Lead Arrangers will act as joint lead arrangers and joint bookrunners for the Facilities. It is agreed that MSSF will have “left placement” and MLPFS will have “right placement” on the top line in the Confidential Information Memorandum referred to below and in all other marketing materials or advertisements related to the Facilities (or, in the case of any such materials or advertisements solely in respect of the Bridge Facility, MLPFS will have “left placement” and MSSF will have “right placement” on the top line thereof). You agree that no other agents, co-agents, co-managers, bookrunners or arrangers will be appointed, no other titles will be awarded and no compensation (other than that expressly contemplated by the Term Sheet and the Fee Letters referred to below) will be paid in connection with the Facilities unless you and we shall so agree; provided that, in consultation with us, you may appoint prior to May 1, 2011, up to two additional joint bookrunners in respect of the Bridge Facility (the “Additional Bookrunners”) so long as each such bookrunner assumes a commitment in respect of no less than 10% of the aggregate principal amount of the Bridge Facility pursuant to a joinder or amendment to this Commitment Letter in form and substance reasonably acceptable to you and us (subject to an aggregate maximum commitment of the Additional Bookrunners in respect of the Bridge Facility not to exceed 20% thereof) (and shall have agreed to become a Lender in the general syndication of the Revolving Credit Facility and the Term Loan A Facility in an aggregate amount as shall be mutually agreed between you and us), it being understood that the commitments of MSSF and BANA in respect of the Bridge Facility shall be ratably reduced by any commitments assumed by any Additional Bookrunner, and it is agreed that such Additional Bookrunners will be listed alphabetically on the second line in the Confidential Information Memorandum referred to below and in all other marketing materials or advertisements related to the Bridge Facility.

The Lead Arrangers intend to syndicate the Facilities (including, in our discretion, all or part of each Commitment Party’s commitment hereunder) to a syndicate of financial institutions identified by the Lead Arrangers in consultation with you (together with MSSF and BANA, the “Lenders”); provided that notwithstanding the Lead Arrangers’ right to syndicate the Facilities and receive commitments with respect thereto, other than with respect to the commitments allocated to, and assumed by, the Additional Bookrunners under the Bridge Facility as described in the preceding paragraph, (i) the Commitment Parties shall not be relieved, released or novated from their respective obligations hereunder (including their obligation to fund the Facilities on the Closing Date) in connection with any syndication, assignment or participation of the Facilities, including its commitments in respect thereof, until after the Closing Date has occurred, (ii) no assignment or novation shall become effective with respect to all or any portion of the Commitment Parties’ commitments in respect of the Facilities until the initial funding of the Facilities, (iii) unless you otherwise agree in writing, the Commitment Parties shall retain exclusive control over all rights and obligations with respect to its commitments in respect of the Facilities, including all rights with respect to consents, modifications, supplements, waivers and amendments, until the Closing Date has occurred and (iv) your consent shall be required with respect to any assignment if, prior to the first anniversary of the Closing Date, the Commitment Parties and the Additional Bookrunners would hold, in the aggregate, less than a majority of the outstanding loans under the Bridge Facility. The Lead Arrangers intend to commence syndication efforts promptly upon the execution of this Commitment Letter, and until the earlier of (x) the date of completion of a Successful Syndication (as

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defined in the Fee Letter) and (y) the date that is 90 days after the Closing Date (such earlier date, the “Syndication Date”), you agree actively to assist, and to use your commercially reasonable efforts to cause the Target to actively assist, the Lead Arrangers in completing the syndication. Such assistance shall include (a) your using commercially reasonable efforts to ensure that the syndication efforts benefit materially from your and, to the extent practical and appropriate, the Target’s existing lending relationships, (b) direct contact between senior management and advisors of the Borrower (and using your commercially reasonable efforts to arrange for direct contact between senior management and advisors of the Target) and the proposed Lenders at times and locations mutually agreed upon, (c) the hosting, with the Lead Arrangers, of one or more meetings of prospective Lenders at times and locations mutually agreed upon and (d) as set forth below, assistance in the preparation of customary materials to be used in connection with the syndication (collectively with the Term Sheet, the “Information Materials”). The Borrower shall use commercially reasonably efforts to obtain, at its expense, corporate credit or family ratings of the Borrower after giving effect to the Transaction and monitored public ratings of the Senior Secured Facilities and the Senior Notes from each of Moody’s Investor Service, Inc. and Standard and Poor’s Rating Services, a division of The McGraw Hill Companies, Inc. for the Borrower, the Senior Secured Facilities and the Senior Notes no later than the Marketing Period Commencement Date (as defined in the Bridge Term Sheet). The Borrower shall participate actively in the process of securing such ratings, including, having senior management of the Borrower meet with such ratings agencies. The Borrower shall also cause senior management of the Borrower and other representatives to participate in any customary “roadshow” in connection with the placement of the Senior Notes during the Marketing Period (as defined in the Bridge Term Sheet). Notwithstanding anything to the contrary contained in the Commitment Letter or the Fee Letters but subject to the Syndication Period Condition (as defined below), none of the completion of the syndication of the Facilities, a Successful Syndication or the receipt of any ratings shall constitute a condition precedent to the availability of the Facilities on the Closing Date.

You will assist us in preparing Information Materials, including Confidential Information Memoranda, for distribution to prospective Lenders. If requested by the Lead Arrangers, you also will assist us in preparing an additional version of the Information Materials (the “Public-Side Version”) to be used by prospective Lenders’ public-side employees and representatives (“Public-Siders”) who do not wish to receive material non-public information (within the meaning of United States federal securities laws) with respect to the Borrower, the Target, their respective affiliates and any of their respective securities (“MNPI”) and who may be engaged in investment and other market related activities with respect to any such entity’s securities or loans. Before distribution of any Information Materials, you agree to execute and deliver to us (i) customary authorization letters authorizing distribution of the Information Materials to a prospective Lender’s employees willing to receive MNPI (“Private-Siders”) and (ii) a separate customary letter authorizing distribution of the Public-Side Version to Public-Siders and represent that no MNPI is contained therein. Each Confidential Information Memorandum will be accompanied by a customary disclaimer exculpating us with respect to any use thereof and of any related Information Materials by the recipients thereof.

The Borrower agrees that the following documents may be distributed to both Private-Siders and Public-Siders, unless the Borrower advises the Lead Arrangers in writing (including by email) within a reasonable time prior to their intended distribution that such materials should only be distributed to Private-Siders: (a) administrative materials prepared by the Lead Arrangers and the Commitment Parties for prospective Lenders (such as a lender meeting invitation, lender allocations and funding and closing memoranda), (b) notification of changes in the terms of the Facilities and (c) other materials intended for prospective Lenders after the initial distribution of Information Materials. If you advise us that any of the foregoing should be distributed only to Private-Siders, then Public-Siders will not receive such materials without further discussions with you.

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The Borrower hereby authorizes the Lead Arrangers and the Commitment Parties to distribute drafts of definitive documentation with respect to the Facilities to Private-Siders and Public-Siders.

The parties hereto agree that information and materials may be distributed or sent through electronic means (including IntraLinks, SyndTrak or another electronic workspace) and that the use of such means is expressly authorized hereby.

You agree that you are responsible for the contents of any Information Materials and you acknowledge that the Lead Arrangers will be using and relying upon such information without independent verification thereof. You agree that such Information Materials may be disseminated to potential Lenders and other persons through one or more Internet sites created for purposes of syndicating the Facilities or otherwise in accordance with the Lead Arrangers’ standard syndication practices.

The Lead Arrangers will manage (in consultation with you) all aspects of the syndication, including decisions as to the selection of institutions to be approached and when they will be approached, when their commitments will be accepted, which institutions will participate, the allocations of the commitments among the Lenders and the amount and distribution of fees among the Lenders. The Lead Arrangers will have no responsibility other than to arrange the syndication as set forth herein and the Lead Arrangers shall in no event be subject to any fiduciary or other implied duties. Additionally, the Borrower acknowledges and agrees that the Lead Arrangers are not advising the Borrower as to any legal, tax, investment, accounting or regulatory matters in any jurisdiction. The Borrower shall consult with its own advisors concerning such matters and shall be responsible for making its own independent investigation and appraisal of the transactions contemplated hereby, and the Lead Arrangers shall have no responsibility or liability to the Borrower with respect thereto. Any review by the Lead Arrangers of the Borrower, the transactions contemplated hereby or other matters relating to such transactions will be performed solely for the benefit of the Lead Arrangers and the Commitment Parties and shall not be on behalf of the Borrower.

To assist the Lead Arrangers in their syndication efforts, you agree promptly to prepare and provide to the Lead Arrangers and the Commitment Parties (and use commercially reasonable efforts to cause the Target to provide) all information with respect to the Borrower and the Target and their respective subsidiaries, the Transaction and the other transactions contemplated hereby, including all financial information and projections (the “Projections”) as we may reasonably request in connection with the arrangement and syndication of the Facilities. You hereby represent and covenant that (a) all written information other than the Projections and information of a general economic or general industry nature (the “Information”) that has been or will be made available to the Lead Arrangers or the Commitment Parties by you or any of your representatives, taken as a whole, is or will be, when furnished, complete and correct in all material respects and does not or will not, when furnished, contain any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements contained therein not materially misleading in light of the circumstances under which such statements are made and (b) the Projections that have been or will be made available to the Commitment Parties or the Lead Arrangers by you or any of your representatives have been or will be prepared in good faith based upon assumptions that are believed by the preparer thereof to be reasonable at the time made; it being understood and agreed that such Projections are not to be viewed as facts and that actual results during the period or periods covered by any such Projections may differ significantly from the projected results, and no assurance can be given that the projected results will be realized. You agree that, if at any time prior to the Syndication Date, you become aware that any of the representations and warranties in the preceding sentence would be incorrect in any material respect if the Information and Projections were being furnished, and such representations were being made, at such time, then you will promptly supplement the Information and the Projections from time to time until the Closing Date and, if requested by the Lead Arrangers, for a reasonable period thereafter through the Syndication Date so that the representation and

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warranty in the preceding sentence remains correct in all material respects. Solely as they relate to matters with respect to the Target and its subsidiaries, the foregoing representations and warranties are limited to such matters as are within your knowledge. You understand that in arranging and syndicating the Facilities we may use and rely on the Information and Projections without independent verification thereof.

As consideration for each Commitment Party’s commitment hereunder and each Lead Arranger’s agreement to perform the services described herein, you agree to pay to the Commitment Parties and the Lead Arrangers the nonrefundable fees set forth in the Fee Letters dated the date hereof and delivered herewith (the “Fee Letters”).

Each Commitment Party’s commitment hereunder and each Lead Arranger’s agreement to perform the services described herein are subject solely to (a) there not having been (i) since January 1, 2011, except (x) as disclosed in the Target’s Annual Report on Form 10-K for the fiscal year ended January 1, 2011 or in any Company SEC Report (as defined in the Acquisition Agreement) filed subsequent to such Form 10-K but prior to the date of the Acquisition Agreement, but excluding any disclosures set forth in any risk factor section and any general statements which, in each case, are cautionary, predictive or forward-looking in nature, or (y) as set forth in the section of the disclosure letter dated the date of the Acquisition Agreement and delivered by the Target to the Borrower with respect to the Acquisition Agreement prior to the date of the Acquisition Agreement (the “Disclosure Letter”) that specifically corresponds to Section 3.06 of the Acquisition Agreement (or in any other section of the Disclosure Letter if the applicability of such disclosure to Section 3.06 of the Acquisition Agreement is reasonably apparent on its face), a Target Material Adverse Effect that would have given you (or your affiliates) the right to terminate the Acquisition Agreement in accordance with its terms or (ii) since April 10, 2011, a Target Material Adverse Effect that is continuing on the Closing Date; provided that for purposes hereof, “Target Material Adverse Effect” means any occurrence, change, event, effect or circumstance that, individually or in the aggregate, (A) is or would be reasonably expected to be, materially adverse to the business, properties, assets, results of operations or financial condition of the Target and its Subsidiaries (as defined in the Acquisition Agreement), taken as a whole, other than any occurrence, change, event, effect or circumstance to the extent relating to or resulting from (i) changes, after the date hereof, in general economic conditions or securities or financial markets in general other than such changes that have a disproportionate effect on the Target as compared to other participants in the medical device industry, (ii) changes, after the date hereof, in Law or GAAP (each as defined in the Acquisition Agreement) or the interpretation thereof other than such changes that have a disproportionate effect on the Target as compared to other participants in the medical device industry, (iii) general changes, after the date hereof, in the medical device industry other than such changes that have a disproportionate effect on the Target as compared to other participants in the medical device industry, (iv) conditions arising out of any outbreak or escalation of hostilities or war (whether declared or not declared), act of terrorism, political conditions, weather conditions or other natural disasters, (v) any actions taken, or failure to take action (other than actions taken or failures to act required by the terms of the Acquisition Agreement), to which the other party to the Acquisition Agreement has expressly consented or requested after the date hereof, (vi) the failure of the Target to meet projections of earnings, revenues or other financial measures (whether such projections were made by the Target or independent third parties), in and of itself (provided, that the underlying causes of such failure (unless otherwise excepted by this clause (A)) may be considered in determining whether a Target Material Adverse Effect has occurred), (vii) any change in the Target’s stock price or trading volume, in and of itself (provided, that the underlying causes of such change (unless otherwise excepted by this clause (A)) may be considered in determining whether a Target Material Adverse Effect has occurred), (viii) the determination by, or the delay of a determination by, the United States Food and Drug Administration (the “FDA”) or any other Governmental Entity (as defined in the Acquisition Agreement), or any panel or advisory body empowered or appointed thereby, in each case, after the date of the Acquisition

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Agreement, with respect to the approval or non-approval of any of the Targets’s or its Subsidiaries’ products which have not, as of the date of the Acquisition Agreement, been approved or cleared by the FDA or any other Governmental Entity, (ix) any legal proceedings made or brought by any of the current or former securityholders of the Target (on their own behalf or on behalf of the Target) arising out of or related to the Acquisition Agreement or any of the transactions contemplated hereby, or (B) would, or would be reasonably expected to, prevent or impair the ability of the Target or any of its Subsidiaries to consummate the Merger (as defined in the Acquisition Agreement) and the transactions contemplated by the Acquisition Agreement prior to October 10, 2011, (b) our satisfaction that prior to the Closing Date there shall be no competing offering, placement or arrangement of any debt securities or bank financing, in each case other than (i) during the period prior to April 20, 2011, the syndication and closing of an up to $250,000,000 senior secured revolving credit facility evidenced by a credit agreement in substantially the form presented to the Lead Arrangers on April 10, 2011, with such amendments, supplements or other modifications thereafter (whether in such credit agreement, pursuant to a separate agreement or otherwise) not materially adverse to the Lenders or the Borrower (it being understood that any increase in the aggregate commitments in excess of $250,000,000 thereunder shall be deemed to be materially adverse to the Lenders and the Borrower) (the “Proposed Target Credit Facility”) so long as prior to or concurrently with the effectiveness of the Proposed Target Credit Facility (w) if there are any amounts then outstanding under the Credit and Guaranty Agreement, dated as of July 20, 2006, among the Target, certain guarantors, certain lenders and CIT Healthcare LLC, as administrative agent (the “Existing Target Credit Agreement”), the Borrower shall use its reasonable best efforts to obtain a customary payoff letter confirming that all indebtedness under the Existing Target Credit Agreement shall have been fully repaid (except to the extent being so repaid with the proceeds of the initial loans and to the extent outstanding letters of credit are continued under the Proposed Target Credit Facility), (x) all outstanding indebtedness and other obligations under the Existing Target Credit Agreement shall in fact have been paid in full, (y) all commitments under the Existing Target Credit Agreement shall have been terminated and cancelled and (z) all liens in connection therewith shall have been terminated and released, (ii) the Senior Notes or any other Securities or (iii) indebtedness of the Target or its subsidiaries permitted to be incurred under Section 5.01(e)(i) of the Acquisition Agreement (as in effect on the date of this Commitment Letter), by or on behalf of the Borrower, the Target or any subsidiary thereof that could materially and adversely disrupt the syndication of the Facilities, (c) the negotiation, execution and delivery on or before the Termination Date (as defined below) of definitive financing documentation with respect to the Facilities (the “Credit Documentation”) to be based upon and otherwise consistent with the applicable Term Sheet, (d) the Lead Arrangers having been afforded a period of 15 consecutive business days (provided that such period shall end before August 22, 2011 or commence after September 6, 2011) from the date of commencement of syndication to syndicate the Facilities (such commencement to occur on the date the final Information Materials are delivered by the Borrower to the Lead Arrangers) (the “Syndication Period Condition”), and (e) solely with respect to the Senior Secured Facilities, the other conditions set forth in Part IV of the Senior Term Sheet under the heading “Certain Conditions” and, solely with respect to the Bridge Facility, the other conditions set forth in Section 4 of the Bridge Term Sheet under the heading “Certain Conditions.” As used herein, “Termination Date” means the date that is six (6) months from the date of this Commitment Letter. The terms of each Commitment Party’s commitment hereunder and of the Facilities are not limited to those set forth herein and in the Term Sheet; it being understood that there are no conditions (implied or otherwise) to the commitments hereunder (including compliance with the terms of the Commitment Letter, the Fee Letters and the Credit Documentation) other than those that are expressly stated to be conditions to the initial funding under the Facilities on the Closing Date (and upon satisfaction (or written waiver by the Commitment Parties) of such conditions, the initial funding under the Facilities shall occur). Those matters that are not covered by the provisions hereof and of the Term Sheet shall be consistent with the Term Sheet in all material respects and otherwise subject to the approval and agreement of each Commitment Party, each Lead Arranger and the Borrower.

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Notwithstanding anything in this Commitment Letter, the Fee Letters, the Credit Documentation or any other letter agreement or other undertaking concerning the financing of the transactions contemplated hereby to the contrary, (a) the only representations relating to you and your subsidiaries, the Target and its subsidiaries, and each of their respective businesses and securities, the accuracy of which shall be a condition to availability of the Facilities on the Closing Date, shall be (i) such representations made (x) by the Target in the Acquisition Agreement as are material to the interests of the Lenders, but only to the extent that you (or your affiliates) have the right to terminate your (or their) obligations (or to refuse to consummate the Acquisition) under the Acquisition Agreement as a result of a breach of such representations and (y) by the Borrower in the Acquisition Agreement as are material to the interests of the Lenders, but only to the extent that the Target (or its affiliates) has the right to terminate its (or their) obligations (or to refuse to consummate the Acquisition) under the Acquisition Agreement as a result of a breach of such representations (collectively, the “Acquisition Agreement Representations”) and (ii) the Specified Representations (as defined below) and (b) the terms of the Credit Documentation shall be in a form such that they do not impair availability of the Facilities on the Closing Date if the conditions set forth in this Commitment Letter are satisfied or waived by the Commitment Parties (it being understood that, to the extent any guarantee or security interest in any collateral (including the creation or perfection of any security interest) referred to in the Senior Term Sheet is not or cannot reasonably be provided or perfected on the Closing Date (other than (x) any guarantee by a Guarantor (as defined in the Senior Term Sheet) that is organized in the United States, (y) the grant and perfection of security interests (i) in assets with respect to which a lien may be perfected solely by the filing of a financing statement under the Uniform Commercial Code (“UCC”) or (ii) in capital stock of the Borrower and the Target and their respective domestic subsidiaries (except to the extent owned by any unrestricted subsidiary) with respect to which a lien may be perfected by the delivery of a stock certificate unless, with respect to this clause (ii), reasonably satisfactory arrangements for timely post-closing delivery thereof shall have been agreed with the Administrative Agent and (z) the filing of short-form security agreements or confirmatory grants with the United States Patent and Trademark Office or the United States Copyright Office, as applicable, with respect to intellectual property collateral) after your use of commercially reasonable efforts to do so or without undue delay, burden or expense, then the provision of any such guarantee and/or the grant or perfection of any such security interest shall not constitute a condition precedent to the availability of the Facilities on the Closing Date, but may instead be provided after the Closing Date pursuant to arrangements and timing to be mutually agreed). For purposes hereof, “Specified Representations” means the representations and warranties referred to in the Term Sheet relating to corporate existence, power and authority (as related to the entering into and performance of the Credit Documentation), due authorization and execution and delivery of the Credit Documentation, no conflicts of the Credit Documentation in any material respect with laws or charter documents, enforceability of the Credit Documentation, effectiveness, validity and perfection of first priority liens (with exceptions to be agreed upon consistent with the Existing Credit Agreement) under the security documents (subject to the limitations set forth in the preceding sentence), solvency of the Borrower and its subsidiaries on the Closing Date on a consolidated basis after giving effect to the Transaction (in a form substantially similar to the solvency certificate delivered by you in connection with the Existing Credit Agreement), status of the Facilities as senior debt, Federal Reserve margin regulations, the Investment Company Act and the Patriot Act. Notwithstanding anything in this Commitment Letter, the Fee Letters, the Credit Documentation or any other letter agreement or other undertaking concerning the financing of the transactions contemplated hereby to the contrary, the only conditions to availability of the Facilities on the Closing Date are set forth in this paragraph and, solely with respect to the Senior Secured Facilities, Part IV of the Senior Term Sheet under the heading “Initial Conditions” and, solely with respect to the Bridge Facility, those in Section 4 of the Bridge Term Sheet under the heading “Certain Conditions.” This paragraph and the provisions herein shall be referred to as the “Certain Funds Provision.”

You agree (a) to indemnify and hold harmless each Commitment Party, each Lead Arranger and their respective affiliates and their respective officers, directors, employees, advisors, affiliates, agents and

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controlling persons (each, an “indemnified person”) from and against any and all losses, claims, damages and liabilities to which any such indemnified person may become subject arising out of or in connection with this Commitment Letter, the Fee Letters, the Facilities, the use of the proceeds thereof or any related transaction or any claim, litigation, investigation or proceeding relating to any of the foregoing, regardless of whether any indemnified person is a party thereto and whether commenced by you or by any third party, and to reimburse each indemnified person upon demand for any reasonable legal or other reasonable out-of-pocket expenses incurred in connection with investigating or defending any of the foregoing, provided that the foregoing indemnity will not, as to any indemnified person, apply to losses, claims, damages, liabilities or related expenses to the extent they are found by a final, non-appealable judgment of a court of competent jurisdiction to arise from (x) the willful misconduct or gross negligence of such indemnified person or any Related Indemnified Person (as defined below) of such indemnified person or (y) a material breach in bad faith by the relevant indemnified person of the express contractual obligations of such indemnified person under this Commitment Letter or the Credit Documentation pursuant to a claim made by the Borrower and (b) to reimburse the Lead Arrangers and their affiliates on demand for all reasonable and documented out-of-pocket expenses (including due diligence expenses, syndication expenses, electronic distribution expenses, travel expenses, consultants’ fees and expenses, and reasonable fees, charges and disbursements of one primary counsel and of any special and local counsel to the Lead Arrangers in connection with the Facilities) incurred in connection with the Facilities and any related documentation (including this Commitment Letter, the Term Sheet, the Fee Letters and the definitive financing documentation) or the administration, amendment, modification or waiver thereof. No indemnified person shall be liable (a) for any damages arising from the use by others of Information or other materials obtained through electronic telecommunications or other information transmission systems other than for direct or actual damages resulting from the gross negligence or willful misconduct of such indemnified person or any Related Indemnified Person of such indemnified person as determined in a final, non-appealable judgment by a court of competent jurisdiction or (b) for any special, indirect, consequential or punitive damages in connection with the Facilities. For purposes hereof, a “Related Indemnified Person” of an indemnified person means (1) any controlling person or controlled affiliate of such indemnified person, (2) the respective directors, officers, or employees of such indemnified person or any of its controlling persons or controlled affiliates and (3) the respective agents of such indemnified person or any of its controlling persons or controlled affiliates, in the case of this clause (3), acting at the instructions of such indemnified person, controlling person or such controlled affiliate; provided that each reference to a controlled affiliate or controlling person in this sentence pertains to a controlled affiliate or controlling person involved in the negotiation or syndication of this Commitment Letter and the Facilities.

This Commitment Letter shall not be assignable by you without the prior written consent of each Commitment Party and each Lead Arranger (and any purported assignment without such consent shall be null and void), is intended to be solely for the benefit of the parties hereto and the indemnified persons and is not intended to confer any benefits upon, or create any rights in favor of, any person other than the parties hereto and the indemnified persons. Each Commitment Party may assign its respective commitment hereunder, in whole or in part, to any of its affiliates and upon such assignment, such Commitment Party will be released from that portion of its commitment hereunder that has been assigned. Furthermore, the Commitment Parties may assign a portion of their commitment hereunder to a Lender (reasonably acceptable to you) that has entered into an amendment or joinder with respect to this Commitment Letter committing to provide a portion of the Facilities on the terms and conditions set forth in this Commitment Letter (in which case, with your consent prior to the Closing Date (such consent to be given in your sole discretion), our commitments hereunder shall be reduced at such time by an amount equal to the commitment assumed by such Lender). This Commitment Letter may not be amended or waived except by an instrument in writing signed by you, each Commitment Party and each Lead Arranger. This Commitment Letter may be executed in any number of counterparts, each of which shall be an original, and all of which, when taken together, shall constitute one agreement. Delivery of an

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executed signature page of this Commitment Letter by electronic or facsimile transmission shall be effective as delivery of a manually executed counterpart hereof. This Commitment Letter and the Fee Letters are the only agreements that have been entered into among us with respect to the Facilities and set forth the entire understanding of the parties with respect thereto.

This Commitment Letter shall be governed by, and construed and interpreted in accordance with, the law of the State of New York; provided, however, that (i) the interpretation of the definition of “Target Material Adverse Effect” used in this Commitment Letter (and whether or not a “Target Material Adverse Effect” has occurred) and (ii) the determination of the accuracy of any Acquisition Agreement Representations and whether as a result of any inaccuracy thereof you (or your affiliates) or the Target (or its affiliates) have the right to terminate your (or their) or the Target’s (or its affiliates’) obligations under the Acquisition Agreement, in each case shall be governed by, and construed and interpreted in accordance with, the laws of the State of Delaware, without regard to the principles of conflicts of law. The Borrower consents to the exclusive jurisdiction and venue of any state or federal courts sitting in the Borough of Manhattan in the City of New York in any action or proceeding arising out of or relating to the Facilities or the other transactions contemplated by this Commitment Letter or the Fee Letters or the performance of services hereunder or thereunder. Each party hereto irrevocably waives, to the fullest extent permitted by applicable law, (a) any right it may have to a trial by jury in any legal proceeding arising out of or relating to this Commitment Letter, the Term Sheet, the Fee Letters or the transactions contemplated hereby or thereby (whether based on contract, tort or any other theory) and (b) any objection that it may now or hereafter have to the laying of venue of any such legal proceeding in any such court. The Borrower, each Commitment Party and each Lead Arranger irrevocably agrees to waive trial by jury in any suit, action, proceeding, claim or counterclaim brought by or on behalf of any party related to or arising out of the transactions contemplated hereby, this Commitment Letter, the Term Sheet or the Fee Letters or the performance of services hereunder.

This Commitment Letter is delivered to you on the understanding that none of this Commitment Letter, the Term Sheet or the Fee Letters or any of their terms or substance shall be disclosed, directly or indirectly, by you to any other person (including, without limitation, other potential providers or arrangers of financing) except (a) to your affiliates, officers, directors, employees, agents, attorneys, accountants and advisors (and for whom you shall be responsible for any breach by any one of them of this confidentiality undertaking) and, on a confidential basis, those of the Target and the Target itself, in each case on a need-to-know basis (except that the Fee Letters may not be disclosed to the Target or any of its affiliates, officers, directors, employees, agents, attorneys, accountants or advisors; provided, however that you may disclose the Fee Letters redacted in a manner reasonably satisfactory to the Commitment Parties in their sole discretion to the Target and its affiliates, officers, directors, employees, agents, attorneys, accountants and advisors on a confidential and need-to-know basis) or (b) as may be compelled in a judicial or administrative proceeding or as otherwise required by law (in which case you agree, to the extent not prohibited by applicable law, to inform us promptly thereof). Notwithstanding the foregoing, (i) following your acceptance hereof, you may disclose the Term Sheet in any syndication or other marketing materials in connection with the Facilities or in connection with any public filing relating to the Transactions, (ii) following your acceptance of the provisions hereof and return of an executed counterpart of this Commitment Letter to the Lead Arrangers as provided below, you may file a copy of any portion of this Commitment Letter (but not the Fee Letters) in any public record in which it is required by law to be filed, (iii) you may disclose the existence and contents of this Commitment Letter, including the Term Sheet, to any rating agency in connection with the Transactions to the extent necessary to satisfy your obligations or the conditions hereunder and (iv) you may disclose the aggregate fee amounts contained in the Fee Letters as part of Projections, pro forma information or a generic disclosure of aggregate sources and uses related to fee amounts related to the Transactions to the extent customary or required in offering and marketing materials for the Facilities and/or the Senior Notes or in any public filing relating to the Transactions.

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You acknowledge that each Commitment Party, each Lead Arranger and their affiliates may be providing debt financing, equity capital or other services (including financial advisory services) to other companies in respect of which you may have conflicting interests regarding the transactions described herein and otherwise. None of the Commitment Parties or the Lead Arrangers will use confidential information obtained from you by virtue of the transactions contemplated by this letter or their other relationships with you in connection with the performance by the Commitment Parties and the Lead Arrangers of services for other companies, and will not furnish any such information to other companies. You also acknowledge that each Commitment Party and each Lead Arranger has no obligation to use in connection with the transactions contemplated by this letter, or to furnish to you, confidential information obtained from other companies. You further acknowledge that each Lead Arranger is a full service securities firm and such Lead Arranger may from time to time effect transactions, for its own or its affiliates’ account or the account of customers, and hold positions in its loans, securities or options on loans or securities of the Borrower and its affiliates and of other companies that may be the subject of the transactions contemplated by this Commitment Letter.

Each Commitment Party and each Lead Arranger will (a) use Confidential Information solely for the purpose of providing the services described herein and consummating the transactions contemplated hereby, (b) treat such Confidential Information with the same degree of care as they treat their own confidential information and (c) will otherwise treat such Confidential Information as confidential and not disclose such Confidential Information except that Confidential Information may be disclosed (a) to its affiliates and its and their directors, officers, employees and agents, including accountants, legal counsel and other advisors on a need-to-know basis (it being understood that the persons to whom such disclosure is made will be informed of the confidential nature of such Confidential Information and instructed to keep such Confidential Information confidential), (b) to the extent requested by any regulatory authority, (c) to the extent required by applicable laws or regulations or by any subpoena or similar legal process (in which case you agree, to the extent not prohibited by applicable law, to inform us promptly thereof), (d) in connection with performing the services described herein and consummating the transactions contemplated hereby, (e) in connection with the exercise of any remedies hereunder or any suit, action or proceeding relating to this Commitment Letter, the Fee Letters, the Facilities or the enforcement of rights thereunder, (f) with the prior written consent of the Borrower or (g) to the extent such Confidential Information (i) becomes publicly available other than as a result of a breach of this paragraph or (ii) becomes available to either Commitment Party or Lead Arranger on a nonconfidential basis from a source other than the Borrower. For the purposes of this letter, “Confidential Information” means all information provided in connection with the transactions contemplated by this Commitment Letter received from the Borrower or any of its representatives relating to the Borrower, the Target or their respective subsidiaries or businesses, other than any such information that is available to either Commitment Party or Lead Arranger on a nonconfidential basis prior to disclosure by the Borrower or any of its representatives or that is independently developed by either Commitment Party or Lead Arranger without reference to any Confidential Information. Any person or entity required to maintain the confidentiality of Confidential Information as provided in this Commitment Letter shall be considered to have complied with its obligation to do so if such person or entity has exercised the same degree of care to maintain the confidentiality of such Confidential Information as such person or entity would accord to its own confidential information. The obligations of the Commitment Parties and the Lead Arrangers under this paragraph shall remain in effect until the earlier of (i) one year from the date of termination of the commitments and agreements of the Commitment Parties and the Lead Arrangers hereunder and (ii) the date the Credit Documentation becomes effective, at which time any confidentiality undertaking in the Credit Documentation shall supersede the provisions of this paragraph.

Each Commitment Party and each Lead Arranger may employ the services of its affiliates in providing services hereunder and, in connection with the provision of such services, may exchange with such affiliates information concerning you and the other companies that may be the subject of the

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transactions contemplated by this Commitment Letter, and, to the extent so employed, such affiliates shall be entitled to the benefits such Commitment Party or Lead Arranger hereunder.

We may, subject to your prior consent (not to be unreasonably withheld, delayed or conditioned) and at our expense, publicly announce as we may choose the capacities in which we or our affiliates have acted hereunder.

The compensation, reimbursement, indemnification and confidentiality provisions contained herein and in the Fee Letters and any other provision herein or therein which by its terms expressly survives the termination of this Commitment Letter shall remain in full force and effect regardless of whether definitive financing documentation shall be executed and delivered and notwithstanding the termination of this Commitment Letter or each Commitment Party’s commitment hereunder; provided that the reimbursement, confidentiality and indemnification provisions hereunder (other than with respect to the confidentiality of the Fee Letters and the contents thereof) shall be superseded by the reimbursement, confidentiality and indemnification provisions of the Credit Documentation upon the effectiveness thereof; provided, further that the syndication provisions set forth herein shall survive any initial funding of the Facilities.

Each Commitment Party and each Lead Arranger hereby notifies you that pursuant to the requirements of the U.S.A. PATRIOT ACT (Title III of Pub. L. 107 56 (signed into law October 26, 2001)) (the “Patriot Act”), it and each of the Lenders may be required to obtain, verify and record information that identifies you, which information may include your name and address and other information that will allow such Commitment Party and such Lead Arranger and each of the Lenders to identify you in accordance with the Patriot Act. This notice is given in accordance with the requirements of the Patriot Act and is effective for each Commitment Party, each Lead Arranger and each of the Lenders.

If the foregoing correctly sets forth our agreement, please indicate your acceptance of the terms hereof and of the Term Sheet and the Fee Letters by returning to MSSF executed counterparts hereof and of the Fee Letters not later than 5:00 p.m., New York City time, on April 11, 2011. Each Commitment Party’s commitment and each Lead Arranger’s agreements herein will expire at such time in the event MSFF has not received such executed counterparts in accordance with the immediately preceding sentence. In the event that the initial borrowing under the Facilities does not occur on or before the Expiration Date, then this Commitment Letter and the commitments hereunder shall automatically terminate. “Expiration Date” means the earliest of (i) the Termination Date, (ii) the closing of the Acquisition without the use of the Facilities and (iii) the termination prior to closing of the Acquisition Agreement in accordance with its terms.

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Each Commitment Party and each Lead Arranger is pleased to have been given the opportunity to assist you in connection with this important financing.

Commitment Letter

Exhibit A

PROJECT KANSAS

SENIOR SECURED FACILITIES

Summary of Terms and Conditions

April 10, 2011

Capitalized terms used but not defined in this Exhibit A shall have the meanings set forth in the Commitment Letter to which this Exhibit A is attached.

Endo Pharmaceuticals Holdings Inc. (the “Borrower”) intends to acquire (the “Acquisition”) a company previously identified to us and code-named “Kansas” (the “Target”), all as previously described to the Commitment Parties and the Lead Arrangers. In connection therewith: (a) the Borrower will enter into an Agreement and Plan of Merger (in form and substance reasonably acceptable to the Lead Arrangers and Commitment Parties) by and among the Borrower, the Target and NIKA Merger Sub, Inc. (together with all exhibits, schedules and disclosure letters thereto, the “Acquisition Agreement”) pursuant to which a subsidiary of the Borrower will merge with and into the Target, with the Target surviving as a wholly-owned subsidiary of the Borrower and (b) the Borrower will obtain the Facilities described in the Commitment Letter. The Lead Arrangers and the Commitment Parties acknowledge and agree that the Acquisition Agreement delivered to them on April 10, 2011 and identified to them as the “execution copy”, together with all exhibits, schedules and disclosure letters thereto delivered to them at 1:50 a.m. (Eastern time) on April 11, 2011, is reasonably acceptable to each of them.

The Acquisition and other transactions described above are collectively referred to herein as the “Transaction”.

Set forth below is a summary of the terms and conditions for the Senior Secured Facilities.

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Annex I

Interest and Certain Fees

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Annex I-A

Pricing Grid

Revolving Credit Facility and Term Loan A Facility

Term Loan B Facility

If at any time the Borrower fails to deliver the quarterly or annual financial statements or certificates required under the Credit Documentation on or before the date such statements or certificates are due, Level IV (or, in the case of the Term Loan B Facility, Level II) shall be deemed applicable for the period commencing three (3) business days after such required date of delivery and ending on the date which is three (3) business days after such statements or certificates are actually delivered, after which the Pricing Level shall be determined in accordance with the table above as applicable.

Except as otherwise provided in the paragraph below, adjustments, if any, to the Pricing Level then in effect shall be effective three (3) business days after the Administrative Agent has received the applicable financial statements and certificates (it being understood and agreed that each change in Pricing Level shall apply during the period commencing on the effective date of such change and ending on the date immediately preceding the effective date of the next such change).

Notwithstanding the foregoing, Level IV (and, in the case of the Term Loan B Facility, Level II) shall be deemed to be applicable until the Administrative Agent’s receipt of the applicable financial statements for

the Borrower’s second full fiscal quarter ending after the Closing Date and adjustments to the Pricing Level then in effect shall thereafter be effected in accordance with the preceding paragraphs.

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Exhibit B

PROJECT KANSAS

BRIDGE FACILITY

Summary of Terms and Conditions

Set forth below is a summary of the principal terms and conditions for the Bridge Facility. Capitalized terms used but not defined herein shall have the meanings set forth in the Commitment Letter to which this Exhibit B is attached (including any other Term Sheet attached thereto); provided that references herein to the “Fee Letter” shall be deemed to refer to the Fee Letter dated as of the date hereof among the Borrower, MSSF, MLPFS and BANA.

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Annex I to Exhibit B

Summary of Terms and Conditions

of Exchange Notes and Extended Term Loans

Capitalized terms used but not defined herein have the meanings set forth or referred to in the Exhibit B to which this Annex I is attached.

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