<PAGE>   1
                                                                   EXHIBIT 10.14

                        CONFIDENTIAL TREATMENT REQUESTED

     Confidential Portions of This Agreement Which Have Been Redacted Are Marked
With Brackets  ([***]).  The Omitted Material Has Been Filed Separately With The
Securities And Exchange Commission.

                                LICENSE AGREEMENT

     THIS LICENSE AGREEMENT (the "Agreement") is entered into as of the 29th day
of January, 1999, by and between HORIZON PHARMACEUTICAL CORPORATION, a company
incorporated under the laws of Delaware, with its principal place of business at
660 Hembree Parkway, Suite 106, Roswell, Georgia 30076 ("Horizon"), and AMERICAN
HOME PRODUCTS CORPORATION, a company incorporated under the laws of Delaware,
with its principal place of business at Five Giralda Farms, Madison, New Jersey
07940, USA ("AHP"). Both Horizon and AHP are referred to herein individually as
a "Party" and collectively as the "Parties".

     WHEREAS, AHP has rights to certain Know-How (as hereinafter defined) and
Trademarks (as hereinafter defined) relating to the Products (as hereinafter
defined);

     WHEREAS,  Horizon is  qualified  to market  pharmaceutical  products in the
Territory (as hereinafter defined);

     WHEREAS, Horizon desires to engage AHP's or its Affiliate's (as hereinafter
defined) facilities and services to manufacture (a) the Product for distribution
and sale by Horizon, and AHP is willing to enter into a separate manufacturing
and supply agreement contemporaneously herewith; and

     WHEREAS, AHP desires to grant and transfer to Horizon and Horizon desires
to receive a license and other rights and assets under the terms and conditions
set forth herein;

     NOW THEREFORE, in consideration of the foregoing premises and the mutual
promises, covenants and conditions contained in this Agreement, the Parties
agree as follows:

1. DEFINITIONS.

     For the purposes of this Agreement, the capitalized terms hereunder shall
have the meanings defined below:

     1.1  "Affiliate(s)" shall mean, in the case of either Party, any
          corporation, joint venture, or other business entity which directly or
          indirectly controls, is controlled by, or is under common control with
          that Party. "Control", as used in this Section 1.1, shall mean having
          the power to direct, or cause the direction of, the management and
          policies of an entity, whether through ownership of voting securities,
          by contract or otherwise. Notwithstanding the foregoing, for purposes


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          of this Agreement, the term "Affiliate" shall not include subsidiaries
          in which a Party or its Affiliates owns a majority of the ordinary
          voting power to elect a majority of the board of directors but is
          restricted from electing such majority by contract or otherwise, until
          such time as such restrictions are no longer in effect.

     1.2  "Closing" shall have the meaning set forth in Section 3.3 hereof.

     1.3  "Commercially Reasonable Efforts" shall mean efforts and resources
          normally used by a Party for a compound or product owned by it or to
          which it has rights, which is of similar market potential at a similar
          stage in its product life, taking into account the competitiveness of
          the marketplace, the proprietary position of the compound or product,
          the regulatory structure involved, the profitability of the applicable
          products, and other relevant factors.

     1.4  "Customer Contracts" shall mean those contracts and outstanding bids
          listed in Exhibit A hereto, between AHP or its Affiliates and certain
          Third Parties pursuant to which such Third Parties, inter alia,
          purchase Products from AHP or such Affiliates in the Territory.

     1.5  "Effective Date" shall mean the date on which the Closing occurs in
          accordance with Section 3.3 hereof.

     1.6  "Field" shall mean use in humans, excluding injectable forms of the
          Substance for human use.

     1.7  "HSR Act" means the Hart-Scott-Rodino Antitust Improvements Act of
          1976, as amended, and the rules and regulations promulgated
          thereunder.

     1.8  "Know-How" shall mean all proprietary technical and clinical
          information, data and know-how relating to the Products, whether or
          not patentable, owned as of the Effective Date or acquired during the
          term of this Agreement, by AHP or its Affiliates. Know-How shall
          include, without limitation, all processes, formulas, discoveries and
          inventions whether relating to biological, chemical, pharmacological,
          toxicological, pharmaceutical, physical and analytical safety, quality
          control and clinical data, including, without limitation, phase IV
          clinical study data. Know-How shall also include relevant medical
          information relating to the Products (such as customer questions,
          responses thereto and adverse drug event (ADE) history) in AHP's
          possession. The term "Know-How", however, shall not include (i) any
          know-how, processes, information and data which is, as of the
          Effective Date or later becomes, generally available to the public or
          (ii) any general manufacturing know-how not specific to the Products.

     1.9  "Letter of Intent" shall mean that certain Letter of Intent which (i)
          is dated as of December 14, 1998 and (ii) relates to the transaction
          contemplated by this Agreement.


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     1.10 "Net Sales" shall mean amounts invoiced for sales of the Products by
          Horizon, its Affiliates and sublicensees to Third Parties in the
          Territory, less the sum of (i) trade, quantity and cash discounts
          actually allowed or paid, (ii) credits or allowances given or made for
          return of previously sold products, (iii) rebates and chargebacks
          specifically identified to the sale of the Products by Horizon, its
          Affiliates and sublicensees, and (iv) taxes, duties or other
          governmental charges levied on or measured by the billing amount, as
          adjusted for rebates and refunds. Such amounts shall be determined
          from the books and records of Horizon, its Affiliates and sublicensees
          which shall be maintained in accordance with generally accepted
          accounting principles. Sales of Products by and between Horizon, its
          Affiliates and sublicensees are not sales to Third Parties and shall
          be excluded from Net Sales calculations for all purposes.

     1.11 "Product(s)" shall mean those Products listed in Exhibit B, for use in
          the Field, each of which have been marketed by AHP as of the date this
          Agreement was signed by the Parties.

     1.12 "Product Supply Agreement" shall have the meaning set forth in Section
          7.1 hereof.

     1.13 "Regulatory Approval" shall mean all authorizations by the appropriate
          Regulatory Authorities which are required for the manufacture (other
          than manufacturing facilities licenses, approvals or authorizations)
          marketing, promotion, pricing and sale of the Products in the
          Territory, including an approved New Drug Application(s) for the
          Product(s) which are owned by AHP or its Affiliates.

     1.14 "Regulatory Authority" shall mean any national, supra-national,
          regional, state or local regulatory agency, department, bureau,
          commission, council or other governmental entity in the Territory
          involved in the granting of Regulatory Approvals for the Product
          including, without limitation, the United States Food and Drug
          Administration ("FDA").

     1.15 "Substance" shall mean the chemical substance 3-[(cyclopentylhydroxy
          phenyl acetyl) oxy] -1, 1-dimethyl (pyrrolidinium bromide, otherwise
          known as glycopyrrolate).

     1.16 "Supply Price" shall mean the price paid by Horizon to AHP under the
          Product Supply Agreement for the purchase of a unit of Product.

     1.17 "Systems Transfer Plan" shall have the meaning set forth in Section
          3.2 hereof.

     1.18 "Territory" shall mean the United States of America, its territories
          and possessions, and the Commonwealth of Puerto Rico.


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     1.19 "Third Party(ies)" shall mean any person(s) or entity(ies) other than
          Horizon, AHP, or their respective Affiliates.

     1.20 "Trademarks" shall mean the trademarks listed on Exhibit C hereto,
          which, as of the date this Agreement was signed by the Parties, has
          been used by AHP in connection with the promotion, marketing and sale
          of the Products.

     1.21 "Transaction Agreements" shall mean this Agreement and the Product
          Supply Agreement.

     1.22 "$" shall mean United States Dollars.

2. RIGHTS GRANTED.

     2.1 Licenses.

            2.1.1 License of Know-How. Subject to the terms and conditions
                  contained in this Agreement, AHP, as of the Effective Date,
                  hereby grants to Horizon an exclusive license (exclusive, even
                  as to AHP, subject to the provisions of Section 2.3), under
                  the Know-How to make, have made, use, market, distribute,
                  offer for sale and sell the Product in the Territory. Horizon
                  accepts all the obligations set forth in this Agreement and
                  agrees to use the Know-How only in connection with the
                  manufacture, sale and promotion of the Products in the
                  Territory, only for so long as the licenses granted under this
                  Section 2.1.1 remain in effect.

            2.1.2 License of Trademark. Subject to the terms and conditions
                  contained in this Agreement, AHP, as of the Effective Date,
                  hereby grants to Horizon an exclusive license (exclusive, even
                  as to AHP), to use the Trademark only in connection with the
                  manufacture, sale and promotion of the Products in the
                  Territory. Horizon accepts all the obligations set forth in
                  this Agreement and agrees to use the Trademark in the
                  Territory, only for so long as the license granted under this
                  Section 2.1.2 remains in effect.

            2.1.3 Sublicenses. Horizon may grant one or more Affiliates or Third
                  Parties sublicenses under the licenses granted to Horizon
                  under Sections 2.1.1 and 2.1.2 in the Territory, provided
                  that:

                  (a)   Horizon obtains AHP's prior written consent, such
                        consent not to be unreasonably withheld;

                  (b)   The parties to and the economic terms of any such
                        agreement shall be fully disclosed to AHP, and the terms
                        of such agreement shall be consistent with all of the
                        relevant terms and provisions of this Agreement;

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                  (c)   To the extent that any such Third Party is to Perform
                        any obligation of Horizon under this Agreement, Horizon
                        shall remain liable for such performance; and

                  (d)   Horizon shall pay AHP the trademark royalties on all Net
                        Sales of Product by such Affiliate or Third Party, as
                        set forth in Section 4.2.1.

     2.2  Assignment of Regulatory Approvals. Subject to the terms and
          conditions contained in this Agreement, AHP shall assign to Horizon at
          the Closing ownership of all its right, title and interest in and to
          the Regulatory Approvals in the Territory. At the Closing, all of
          AHP's obligations under this Agreement with respect to such Regulatory
          Approvals shall immediately terminate (with the exception of
          reporting, as required under Section 6.2 hereof, to Horizon
          significant safety and efficacy issues relating to Product or
          Substance of which AHP is aware and which are required for NDA
          reporting in the United States) and thereafter, AET shall have no
          further right in or to such Regulatory Approvals in the Territory,
          except as provided in Section 6.1.2 hereof Subject to the notice and
          cure provisions of Section 11.2.2, if Horizon fails to pay to AHP the
          entire amount of the License Fee when due, Horizon shall immediately
          reassign the Regulatory Approvals to AHP.

     2.3  Retained Rights. Notwithstanding the licenses granted to Horizon under
          Section 2.1, after the Closing, AHP shall retain ownership of and all
          rights to (i) the current NDC numbers and Product Codes it uses for
          each of the Products (subject to Horizon's right to sell Product under
          Section 2.7 of the Product Supply Agreement), (ii) the real and
          personal property (including, without limitation, all equipment) and
          general manufacturing know-how used by AHP in manufacturing the
          Products (either before, during or after the term of this Agreement)
          other than Know-How, (iii) all accounts receivable from sales of the
          Products by or on behalf of AHP, and (iv) all inventories of the
          Products that have not otherwise been purchased by Horizon pursuant to
          Section 7.1 hereof and the Product Supply Agreement. Additionally, AHP
          retains ownership of and the right to use the Know-How (i) to
          manufacture Products for Horizon pursuant to Section 7.1 hereof and
          the Product Supply Agreement; (ii) to manufacture Products for sale
          outside of the Territory (including, without limitation, for sale to
          AHP's Affiliates or Third Parties in the Territory, for final
          distribution and sale outside of the Territory); (iii) to manufacture
          products containing Substance for use or sale, both in and outside of
          the Territory, as veterinary pharmaceutical products and as injectable
          product for human use; and (iv) to manufacture, use and sell Products
          in the Territory if this Agreement is terminated by AHP pursuant to
          Section 11.2.2 hereof and all payments due to AHP pursuant to Section
          4.1.1 have not been fully paid to AHP.

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     2.4  Horizon's Covenant Not To Compete. Horizon agrees that, during the
          term of this Agreement, Horizon and its Affiliates will not utilize
          the Know-How, Regulatory Approvals or Trademarks in any manner to
          make, have made, use, market, offer to sell or sell any product
          containing the Substance as a pharmaceutically active ingredient for
          use as a veterinary pharmaceutical agent or for injectable dosage
          forms for human use.

3.   PRE-CLOSING ACTIVITIES; CLOSING.

     3.1  Government Approvals. Each of Horizon and AHP shall use its good faith
          efforts to eliminate any concern on the part of any court or
          government authority regarding the legality of the proposed
          transaction, including, if required by state antitrust authorities,
          promptly taking all steps to secure government antitrust clearance,
          including, without limitation, cooperating in good faith with any
          government investigation including the prompt production of documents
          and information demanded by a second request for documents and of
          witnesses if requested. Horizon and AHP will cooperate and use
          respectively all reasonable efforts to make all registrations, filings
          and applications, to give all notices and to obtain by the Closing all
          governmental or other consents, transfers, approvals, orders,
          qualifications, authorizations, permits and waivers, if any, and to do
          all other things necessary or desirable for the consummation of the
          transactions as contemplated hereby. Neither Party shall be required,
          however, to divest products or assets or materially change its
          business if doing so is a condition of obtaining approval under the
          governmental approvals of the transactions contemplated by this
          Agreement.

     3.2  Systems Transfer. During the time period between the signing of this
          Agreement by the Parties and the Closing, the Parties will develop a
          mutually acceptable post Closing operation plan substantially in the
          form of Exhibit D hereto (the "Systems Transfer Plan") to transfer the
          processing of chargebacks, government rebates, returns (including the
          processing of customer credits), obligations under Customer Contracts,
          customer service functions, and regulatory reporting functions from
          AHP to Horizon and Know-How necessary to enable Horizon to use,
          market, distribute and sell Product in the Territory. Such plan shall
          be reduced to writing by Horizon and approved by both Parties and
          shall be implemented by the Parties as soon as practicable after the
          Closing.

     3.3  The Closing.

          3.3.1 Time and Place. The Closing of the transactions contemplated
                hereby shall take place at 10:00 A.M. (local time) on January
                29, 1999 at the offices of Wyeth-Ayerst Laboratories Division
                of American Home Products Corporation, St Davids,
                Pennsylvania, or at such other time and place as the Parties
                may agree. The Closing shall be effective as of midnight on
                the Effective Date.




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                    [***] - CONFIDENTIAL TREATMENT REQUESTED


            3.3.2 Payment of License Fee. At the Closing, Horizon shall make the
                  payment required by Section 4.1(i) hereof, which payment shall
                  be made by wire transfer in funds immediately available to
                  such bank account as AHP may designate at least three (3)
                  business days in advance.

            3.3.3 Customer  Information.  To the extent the following items have
                  not previously been provided to Horizon,  AHP, at the Closing,
                  will deliver to Horizon

                  (a)   complete and accurate copies of AHP's relevant customer
                        lists including relevant sales data for the Products;
                        and

                  (b)   copies of current and pending customer sales contracts
                        for the Product, which contracts shall be redacted for
                        purposes of deleting information that is not related to
                        the Product and other confidential information.

            3.3.4 Other Agreements. At the Closing, Horizon and AHP shall each
                  execute and deliver to the other the Systems Transfer Plan and
                  the Product Supply Agreement in the form attached hereto as
                  Exhibit F.

            3.3.5 Certifications of Representations and Warranties. At the
                  Closing, each Party shall certify to the other that the
                  representations and warranties set forth in Article 10 hereof
                  remain true and in effect as of the day of Closing. In the
                  event that one or more of the representations and warranties
                  do not remain true and in effect as of the day of Closing, the
                  Party receiving such certification shall have the option to
                  (i) complete the Closing (and such Party shall be required to
                  expressly waive its rights under the specific representation
                  and warranty which is no longer true and/or in effect as of
                  the day of closing) or (ii) terminate this Agreement as
                  provided in Section 11.2.1.

      3.4   Conduct of Business from Signing to Closing. AHP covenants and
            agrees that, during the period between the signing of this Agreement
            and Closing, it will use its Commercially Reasonable Efforts to
            conduct the business relating to Product in a manner consistent with
            its prior practices.

4.    CONSIDERATION.

     4.1    License Fee. In partial consideration of the licenses granted to
            Horizon under Section 2.1 hereof and the other rights and assets
            transferred to Horizon hereunder, Horizon shall pay AHP a
            nonrefundable, noncreditable license fee (the "License Fee") as
            follows (i) [***] dollars ($[***]) which shall be due and payable at


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                    [***] - CONFIDENTIAL TREATMENT REQUESTED

            the Closing and (ii) [***] payments each in the amount of [***]
            dollars ($[***]) due [***], for a total of [***] dollars ($[***]) in
            addition to the payment due under Section 4.1(i) above.

     4.2    Royalties.

            4.2.1 Royalty Rates. In further consideration of the trademark
                  license granted to Horizon under Section 2.1.2 hereof, during
                  the term of this Agreement, Horizon shall pay AHP royalties in
                  the amount of

                  (a)   [***] of the Net Sales for all Products sold by or on
                        behalf of Horizon, its Affiliates and sublicensees prior
                        to the [***] anniversary of the Effective Date up to
                        annual Net Sales of $[***]; and

                  (b)   [***] of the Net Sales for all Products sold by or on
                        behalf of Horizon, its Affiliates and sublicensees prior
                        to the [***] anniversary of the Effective Date of Net
                        Sales above annual Net Sales of $[***]; and

                  (c)   [***] of the Net Sales for all Products sold by or on
                        behalf of Horizon, its Affiliates and sublicensees after
                        the [***] anniversary of the Effective Date.

            4.2.2 Minimum Royalties. During the period from the Effective Date
                  to the fifth anniversary of the Effective Date, Horizon shall
                  pay a minimum royalty to AHP each calendar quarter of [***]
                  dollars ($[***]).

            4.2.3 Scope of Royalty Obligations. No royalties shall be due upon
                  the sale or other transfer among Horizon and its Affiliates,
                  but in such cases the royalty shall be due and calculated upon
                  Horizon's or its Affiliates' Net Sales to the first
                  independent Third Party.

            4.2.4 Royalties Paid Quarterly. For each calendar quarter, or part
                  thereof, in which Horizon sells Product and is obligated to
                  pay to AHP royalties with respect to such sales pursuant to
                  this Section 4.2, Horizon shall, for the first four calendar
                  quarters following the Effective Date within forty five (45)
                  calendar days, and for each calendar quarter thereafter within
                  thirty (30) calendar days, following the close of each such
                  calendar quarter furnish to AHP a written report for the
                  calendar quarter showing (i) the number of units of each
                  Product (by NDC number) sold by Horizon, its Affiliates and
                  sublicensees in the Territory during such calendar quarter,
                  (ii) the Net Sales of Product (by NDC number) sold by Horizon,
                  its Affiliates and sublicensees in the Territory during such
                  calendar month, and (iii) the royalties payable under this
                  Agreement for such calendar quarter. Simultaneously with the


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                  submission of the written report, Horizon shall pay to AHP a
                  sum equal to the aggregate royalty due for such calendar
                  quarter calculated in accordance with this Agreement
                  (reconciled for any previous overpayments, underpayments or
                  credits).

     4.3    Method of Payment. All payments to be made by Horizon to AHP
            pursuant to Section 4.2 hereof shall be made in United States
            dollars by wire transfer simultaneously with the submission of the
            report required under Section 4.2.4 hereof.

     4.4    Maintenance of Records by Horizon; Audits.

                  4.4.1    Record Keeping by Horizon. Horizon and its Affiliates
                           shall, and shall cause its sublicensees to, keep
                           accurate books and accounts of record in connection
                           with the sale by or on behalf of Horizon, its
                           Affiliates and sublicensees of the Products in
                           sufficient detail (i) to permit accurate
                           determination of all figures necessary for
                           verification of payments required to be paid
                           hereunder and (ii) to verify compliance with the
                           provisions of Section 8.3 hereof. Horizon, its
                           Affiliates and sublicensees shall maintain such
                           records for a period of three (3) years after the end
                           of the year in which they were generated.

                  4.4.2    Audit by AHP. AHP, through an independent certified
                           public accountant reasonably acceptable to Horizon,
                           shall have the right, at its own expense, to access
                           the books and records of Horizon, its Affiliates and
                           sublicensees as may be reasonably necessary (i) to
                           verify the accuracy of the royalty reports and all
                           payments made hereunder and (ii) to verify compliance
                           with the provisions of Section 8.3 hereof, including,
                           without limitation, the determination of any
                           additional payments that may be due to AHP pursuant
                           to Section 8.3 hereof. Such access shall be conducted
                           after reasonable prior written notice to Horizon and
                           during ordinary business hours and shall not be more
                           frequent than once per calendar year, in respect of
                           any calendar year ending not more than thirty (30)
                           months prior to the date of such notice. Upon the
                           expiration of the thirty (30) month period described
                           in the immediately preceding sentence, the
                           calculation of amounts payable with respect to such
                           time periods shall be binding and conclusive upon
                           AHP, and Horizon, its Affiliates and sublicensees
                           shall be released from any liability or
                           accountability with respect to payments for such time
                           periods. The parties agree that such independent
                           certified public accountant shall disclose to AHP
                           only whether the royalty reports are correct or
                           incorrect, the specific details concerning any
                           discrepancies in such reports, whether the provisions
                           of Section 8.3 hereof have been complied with and the
                           specific details concerning any noncompliance with
                           the provisions of Section 8.3 hereof. AHP agrees to
                           keep in strict confidence all information learned in
                           the course of such


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                           audit, except when it is necessary to reveal such
                           information in order to enforce its rights under this
                           Agreement.

                  4.4.3    Underpayments/Overpayments. If such independent
                           certified public accountant's report shows any
                           underpayment, Horizon shall remit or shall cause its
                           Affiliates and sublicensees to remit to AHP within
                           thirty (30) days after AHP's receipt of such report,
                           (i) the amount of such underpayment (ii) interest on
                           such underpayment at the prime rate quoted by Chase
                           Manhattan Bank N.A. from the date payment was first
                           due until the date of payment of such underpayment
                           and (iii) if such underpayment exceeds five percent
                           (5%) of the total amount owed for the calendar year
                           then being audited, the reasonable fees and expenses
                           of such independent certified public accountant
                           performing the audit. Any overpayments, less the
                           reasonable fees and expenses of such independent
                           certified public accountant, shall be fully
                           creditable against amounts payable in subsequent
                           payment periods.

         4.5      Taxes and Withholding. All taxes levied or incurred on account
                  of any payments from Horizon to AHP accruing under this
                  Agreement, by national, state or local governments, will be
                  assumed and paid by Horizon, except taxes levied thereon as
                  income to AHP and if such taxes are required to be withheld by
                  Horizon they will be deducted from payments due to AHP and
                  will be timely paid by Horizon to the proper taxing authority
                  for the account of AHP, a receipt or other proof of payment
                  therefor secured and sent to AHP as soon as practicable.

5.    DISCLOSURE OF KNOW-HOW; ASSUMPTION OF OBLIGATIONS

     5.1    Disclosure of Know-How. At or immediately after the Closing, in
            accordance with Section 3.2, AHP shall promptly disclose to Horizon
            that Know-How currently utilized by or on behalf of AHP or its
            Affiliates which is necessary to enable Horizon to use, market,
            distribute and sell the Product in accordance with the Transaction
            Agreements.

     5.2    Customer Contracts. A complete and accurate list of each of the
            current and pending Customer Contracts pursuant to which AHP or an
            AHP Affiliate is, with respect to the current Customer Contracts
            immediately prior to the date of this Agreement, selling Products,
            along with other products of AHP and its Affiliates, to Third Party
            buyers is attached hereto as Exhibit A. AHP agrees that between the
            date of signing of this Agreement and Closing, no new Customer
            Contracts shall be executed without first consulting with Horizon.
            AHP further agrees that between the date of signing of this
            Agreement and Closing, no new bids shall be made without first
            consulting with and obtaining the written consent of Horizon. The
            parties agree that bids outstanding as of the date of the signing of
            this Agreement shall be handled in AHP's normal course of business.



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                    [***] - CONFIDENTIAL TREATMENT REQUESTED

            The Parties understand and agree that because the right to sell
            Product is being transferred to Horizon pursuant to this Agreement,
            as of the Effective Date AHP will no longer have the right to sell
            or, except as provided below, adjust the price of Product under the
            Customer Contracts, provided, however, that Horizon agrees that it
            will continue to honor all of AHP's commitments made in each such
            Customer Contract with respect to supplying the Product, including,
            without limitation, the sale prices as adjusted in accordance with
            such Customer Contracts, for the Products throughout the term of
            each such Customer Contract. After the Closing, upon Horizon's
            request, AHP and Horizon will request each Third Party to the
            Customer Contracts to relieve AHP of its obligations to provide
            Product under each such Customer Contract. In addition, to the
            extent that AHP and Horizon are unable to obtain a release from a
            Third Party of AHP's obligations to supply the Product under such
            Customer Contract, then upon the request of Horizon, AHP shall use
            its Commercially Reasonable Efforts to take actions that are
            permitted under the terms of such Customer Contract to minimize the
            commitment for Product thereunder, including without limitation,
            adjusting Product prices, reducing the term of such Customer
            Contract solely with respect to the Product and terminating AHP's
            obligations with respect to Product under any such Customer
            Contract, provided, however, that AHP shall not be required to
            either (i) adjust prices or terms relating to products other than
            Products, (ii) make any payments to such Third Party in
            consideration for making such price adjustments or modifications to
            the Customer Contract or (iii) terminate any such Customer Contract
            with respect to products other than Products. AHP agrees that
            following the signing of this Agreement, it will not take any action
            with respect to any Customer Contract which will extend the term of
            such Customer Contract for any Product or otherwise adversely affect
            Horizon with respect to any Product, without the prior written
            consent of Horizon. All sales of the Product after the Closing shall
            be booked by Horizon.

     5.3    Chargebacks.  As of the Closing, Horizon will be responsible for all
            customer  chargebacks  for Product sold in the Territory,  provided,
            however, that, with respect to such Product sales, AHP, for a period
            of [***] after the Effective  Date,  will reimburse  Horizon for all
            qualified  customer  chargebacks  having Activity Dates prior to the
            Effective  Date.  For purposes of this  Section  5.3, the  "Activity
            Date" is the date a wholesaler ships the Product to a customer under
            terms of a customer  sales  contract or pursuant to a purchase order
            issued by such customer.

      5.4   Rebates. As of the Closing, Horizon will be fully responsible for
            all Federal, State and Third Party rebate programs for Product sold
            in the Territory under Horizon's NDC numbers, including all
            reporting activities associated with such programs. Additionally, as
            of the Closing, Horizon will be financially responsible for all
            Federal, State and Third Party rebate programs for Product sold in
            the Territory under AHP's label, provided, however, that with
            respect to such Product sales, AHP will continue to prepare the


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                    [***] - CONFIDENTIAL TREATMENT REQUESTED


            appropriate Federal and State rebate reports and process Federal and
            State rebates for the sale of such Product and Horizon will
            reimburse AHP for [***]. For purposes of this Section 5.4, the
            "Report Date" is the date a qualified rebate invoice is issued under
            applicable Federal or State Rebate Programs.

      5.5   Returns. As of the Effective Date, Horizon will be responsible for
            all returns of Product sold in the Territory, provided, however,
            that AHP will reimburse Horizon for all qualified returns of such
            Product sold by AHP to Third Parties prior to the Effective Date.
            The Parties agree to track sales and returns of Product by lot
            number to determine whether such Product was sold to Third Parties
            by AHP prior to the Effective Date or by Horizon after the Effective
            Date. AHP's liability pursuant to this Section 5.5 for such returns
            shall not exceed [***] and all returns in excess of such limitation
            shall be borne solely by Horizon.

     5.6    Reimbursement.  AHP shall reimburse Horizon for chargebacks, rebates
            and  returns  according  to  Sections  5.3,  5.4 and 5.5 as follows:
            Horizon  agrees to provide AHP with an invoice for amounts due under
            Sections  5.3, 5.4 and 5.5 within  thirty (30) days after the end of
            each calendar  month with the  documentation  required to verify the
            same.  AHP agrees to reimburse  Horizon in accordance  with Sections
            5.3, 5.4 and 5.5 hereof within thirty (30) days after the receipt of
            the invoice and all required documentation.

6.   REGULATORY MATTERS.

     6.1    Horizon Responsibilities.

            6.1.1   Disclosure of Regulatory Approvals. Within thirty (30) days
                    after the Effective Date, AHP shall provide Horizon with a
                    copy of all correspondence or other documents reasonably
                    related to such Regulatory Approvals. Additionally, within
                    such thirty (30) day period, AHP shall provide to Horizon a
                    current list of suppliers for Materials used in the
                    manufacture of Products.

            6.1.2   Right of Reference.  Horizon  irrevocably  grants to AHP the
                    right to reference the Regulatory Approvals to support AHP's
                    Product related  activities  outside of the Territory and to
                    support any veterinary  pharmaceutical  products  containing
                    Substance or any  injectable  products for human use,  which
                    AHP currently markets or sells or may, in the future, market
                    or sell.  Horizon shall not amend the  Regulatory  Approvals
                    without the prior  written  consent of AHP, such consent not
                    to be  unreasonably  withheld,  and  AHP  shall  respond  to
                    Horizon's  request for consent  within thirty (30) days from
                    such request.


                                       12
<PAGE>   13

            6.1.3 Responsibilities. After the Effective Date, Horizon shall be
                  solely responsible for conducting all activities in connection
                  with such Regulatory Approvals, including, without limitation,
                  communicating and preparing and filing all reports (including,
                  without limitation, adverse drug experience reports) with the
                  appropriate Regulatory Authorities in the Territory and
                  interacting with any Third Parties with respect to Products
                  sold or distributed in the Territory; provided, however, that
                  for up to sixty (60) days after the Effective Date, AHP shall
                  assist and cooperate in the transition of such activities to
                  Horizon. Additionally, to the extent that Horizon is
                  obligated, under applicable laws and regulations, to report to
                  the Regulatory Authorities in the Territory, adverse drug
                  experiences associated with Product sold by or on behalf of
                  AHP outside of the Territory, AHP shall provide Horizon with
                  information about such adverse drug experiences in accordance
                  with the provisions of Section 6.2 hereof and to the extent
                  that, AHP is obligated under applicable laws and regulations
                  to report adverse drug experiences associated with Product
                  sold by or on behalf of Horizon inside the Territory, Horizon
                  shall provide AHP with information about such adverse drug
                  experiences in accordance with the provisions of Section 6.2
                  hereof. Upon written request of Horizon, AHP shall provide
                  Horizon with all additional written information in AHP's
                  possession which directly relates to the Products in the Field
                  as AHP shall have developed and which would be useful in
                  supporting the Regulatory Approvals.

            6.1.4 Payment of Fees. After the Effective Date, Horizon shall pay
                  all NDA maintenance fees and any establishment license fees of
                  Horizon, its Affiliates or Third Parties which must be paid
                  with respect to facilities used in the manufacture of Product
                  by or on behalf of Horizon. Notwithstanding the foregoing, for
                  so long as AHP is supplying Product to Horizon in accordance
                  with the Product Supply Agreement, AHP shall pay any
                  establishment license fees which must be paid with respect to
                  AHP's, its Affiliate's or subcontractor's facilities used for
                  the manufacture of such Product.

      6.2   Adverse Drug Experience Reporting. In order for the Parties to
            comply with their respective responsibilities under this Article 6
            and otherwise relating to the reporting of adverse drug experiences,
            to the extent either Party receives any information regarding
            adverse drug experiences related to the use of the Product, whether
            such use is within or outside of the Territory, such Party shall
            promptly provide the other Party with such information in accordance
            with the Adverse Event Reporting Procedures (as may be amended from
            time to time upon mutual agreement) set forth in Exhibit E.



                                       13
<PAGE>   14

                    [***] - CONFIDENTIAL TREATMENT REQUESTED

7.   SUPPLY.

      7.1   Supply of Product by AHP. For the term set forth in the Product
            Supply Agreement, AHP, either directly or through one or more
            subcontractors, shall manufacture and supply Products to Horizon for
            sale in the Territory and Horizon shall purchase from AHP its entire
            requirements of Products for sale in the Territory, all in
            accordance with the terms and conditions of the Product Supply
            Agreement, in the form attached hereto as Exhibit F, to be entered
            into by the Parties at the Closing.

      7.2   Supply of Product by Horizon. Following the term set forth in the
            Product Supply Agreement and thereafter:

            (a)   Horizon shall be responsible, at its own expense, for
                  manufacturing its requirements of Product, either by itself or
                  through a Third Party;

            (b)   Upon AHP's request, Horizon shall purchase from AHP (i)
                  reasonable quantities of AHP's residual inventories of
                  Products having not less than twelve months remaining dating
                  at the then current purchase price and (ii) reasonable
                  quantities of AHP's useable, residual inventories of Product
                  specific Materials (as defined in the Product Supply
                  Agreement), including, without limitation, all labels and
                  other Product specific packaging materials at AHP's
                  fully-absorbed manufacturing costs;

            (c)   Upon AHP's request, Horizon would supply AHP's requirements of
                  Products for sale by AHPC outside the Territory at Horizon's
                  then fully-absorbed manufacturing cost plus a [***] mark-up,
                  which purchase prices shall be increased once each year by
                  [***].

            (d)   Upon AHP's request, Horizon will use its Commercially
                  Reasonable Efforts to facilitate discussions between AHP and
                  any Third Party manufacturer with which Horizon may be in
                  discussions regarding the manufacture of the Product following
                  the term of the Product Supply Agreement.

     7.3    Supply of Substance by Horizon. Following the term set forth in the
            Product Supply Agreement, and thereafter:

            (a)   Horizon shall be responsible, at its own expense, for
                  manufacturing its requirements of bulk Substance, either by
                  itself or through a Third Party;


                                       14

<PAGE>   15



            (b)   Upon AHP's request, Horizon shall purchase from AHP (i)
                  reasonable quantities of AHP's residual inventories of the
                  bulk Substance and (ii) reasonable quantities of AHP's
                  residual inventories of Substance specific Materials (as
                  defined in the Substance Supply Agreement), including without
                  limitation, all labels and other Substance specific packaging
                  materials, in each case at AHP's fully-absorbed manufacturing
                  costs; and

            (c)   Upon AHP's request, Horizon will use its Commercially
                  Reasonable Efforts to facilitate discussions between AHP and
                  any Third Party manufacturer with which Horizon may be in
                  discussions regarding the manufacture of the Substance
                  following the term of the Product Supply Agreement.

8.   PROMOTION, MARKETING AND SALE OF PRODUCTS.

     8.1    Diligence. As of the Closing, Horizon shall be solely responsible
            for and shall use its Commercially Reasonable Efforts to promote,
            market, sell and distribute the Products in the Territory.

     8.2    Materials and Promotional Claims. Horizon at all times shall be
            solely responsible for complying with all applicable laws and
            regulations in its promotion and marketing of the Products.

     8.3    Timing of Sales. Horizon agrees that it and its Affiliates shall
            not, by any action or act of omission cause sales of Products that
            would have otherwise occurred prior to the end of the fifth
            anniversary of the Effective Date, to occur after the fifth
            anniversary of the Effective Date.

            Such actions or acts of omission may include, without limitation,
            announcing or implementing changes in the price of Products, or
            delaying the filling of orders. AHP shall have the right to audit,
            in accordance with Section 4.5.2 hereof all of Horizon's records
            reasonably necessary to verify compliance with this Section and if
            AHP determines that either Horizon or its Affiliates has taken any
            such actions or committed any such act of omission then, for
            purposes of the payment of royalties under Section 4.2 hereof, the
            Net Sales of Product made during the three months after the fifth
            anniversary of the Effective Date shall be treated as if such sales
            occurred prior to the fifth anniversary of the Effective Date.


                                       15
<PAGE>   16

9.    TRADEMARKS.

      9.1   Use of Trademarks. Horizon agrees to use the Trademarks only in
            connection with the Products and in the manner and style which shall
            have the prior written approval of AHP. Horizon shall submit to AHP
            samples of all commercial materials containing any of the
            Trademarks. AHP, within thirty (30) days of its receipt of such
            materials, shall have the right to reasonably comment on the usage
            of the Trademarks in such materials and Horizon, at its own cost and
            expense, will promptly correct any improper usage of the Trademarks.
            Horizon agrees not to claim or to assert any right of ownership in
            or to such Trademarks or the goodwill associated therewith and shall
            take no action which may destroy, damage or impair in any way the
            ownership or rights of AHP in and to such Trademarks. Horizon shall
            not register anywhere in the world in its own name, or on behalf of
            any other person or entity, any trademark, trade dress, brands,
            labeling, designs or other indicia of ownership identical to, or
            confusingly similar to, the Trademarks, and shall not associate the
            Trademarks with any articles other than the Products and shall, at
            the request of AHP, do all such acts and things and execute all such
            documents as AHP shall in its reasonable discretion consider
            necessary or proper to register or maintain the registration of the
            Trademarks in any country of the Territory. Should usage of the
            Trademarks in any country vest title thereto in Horizon, then
            Horizon shall at AHP's request, immediately assign and transfer such
            title to AHP.

      9.2   Quality Control. Horizon will not permit the quality of Products to
            deteriorate while in its possession so as to adversely affect the
            goodwill associated with the Trademarks. Horizon shall upon request
            of AHP, from time to time furnish AHP, without charge,
            specifications and samples of Products for quality review by AHP.
            AHP or an authorized representative thereof shall have the right, at
            all reasonable times, to inspect the finished goods in relation to
            which the Trademarks are to be used, as part of appropriate quality
            control.

      9.3   Infringement of Trademarks. In the event that, either Horizon or AHP
            learn that any of the Trademarks pertaining to Products is being
            infringed in the Territory by any Third Party, it shall promptly
            notify the other Party of such infringement. AHP shall have the
            right, but not the obligation, to act to terminate any such Third
            Party infringement, including, without limitation, prosecuting a
            lawsuit or other legal proceeding, at AHP's own expense. In the
            event that AHP takes any such action to terminate such infringement,
            Horizon may, at its sole option, take appropriate steps to join AHP
            in such action and share equally in the costs thereof. If and only
            if Horizon joins such action as stated in the preceding sentence,
            AHP and Horizon shall share equally in any recovery which may be
            received as a result of such action less the reimbursement of each
            Party for the out-of-pocket expenses incurred in taking, joining and
            prosecuting such action. Notwithstanding the foregoing, Horizon
            shall fully cooperate with AHP in any action AHP takes to terminate
            such infringement and, to the


                                       16
<PAGE>   17

            extent AHP recovers damages from such Third Party, through
            settlement or otherwise, shall be reimbursed by AHP for all
            reasonable expenses incurred in connection therewith. If AHP fails
            to take any action within sixty (60) days after Horizon's request,
            Horizon shall have the right to act as it sees fit to terminate the
            infringement, including without limitation, prosecuting a lawsuit or
            other legal proceeding, at Horizon's own expense. Horizon may deduct
            its costs and expenses for such action from trademark royalties
            accruing under Section 4.2 after the date of filing of such action.
            In the event that Horizon takes any such action to terminate such
            infringement, AHP may, at its sole option, take appropriate steps to
            join Horizon in such action and share equally in the costs thereof.
            If and only if AHP joins such action as stated in the preceding
            sentence, AHP and Horizon shall share equally in any recovery which
            may be received as a result of such action less the reimbursement of
            each Party for the out-of-pocket expenses incurred in taking,
            joining and prosecuting such action. Notwithstanding the foregoing,
            AHP shall fully cooperate with Horizon in any action Horizon takes
            to terminate such infringement, including without limitation,
            agreeing to be joined as party plaintiff and approving any
            reasonable settlement agreement achieved by Horizon, and to the
            extent Horizon receives damages from such Third Party, through
            settlement or otherwise, shall be reimbursed by Horizon for all
            reasonable expenses incurred in connection therewith and deductions
            from trademark royalties pursuant to this Section 9.3.

10.  REPRESENTATIONS AND WARRANTIES.

     10.1   Representations and Warranties of Each Party. As of the signing of
            this Agreement, each of Horizon and AHP hereby represents, warrants
            and covenants to the other Party hereto as follows:

            (a)     it is a corporation or entity duly organized and validly
                    existing under the laws of the state or other jurisdiction
                    of incorporation or formation;

            (b)     the execution, delivery and performance of this Agreement by
                    such Party has been duly authorized by all requisite
                    corporate action and do not require any shareholder action
                    or approval;

            (c)     it has the power and authority to execute and deliver this
                    Agreement and to perform its obligations hereunder;

            (d)   the execution, delivery and performance by such Party of this
                  Agreement and its compliance with the terms and provisions
                  hereof does not and will not conflict with or result in a
                  breach of any of the terms and provisions of or constitute a
                  default under (i) a loan agreement, guaranty, financing
                  agreement, agreement affecting a product or other agreement or
                  instrument binding or affecting it or its property; (ii) the
                  provisions of its charter or operative documents or bylaws; or
                  (iii) any order, writ, injunction or decree of any court or
                  governmental authority entered against it or by which any of
                  its property is bound; and



                                       17
<PAGE>   18

            (e)   it shall at all times comply with all applicable material laws
                  and regulations relating to its activities under this
                  Agreement.

      10.2  Representations and Warranties of AHP. As of the signing of this
            Agreement, AHP hereby represents and warrants to Horizon as follows:

            (a)   Except as listed in Exhibit G, there are no (i) pending or, to
                  AHP's knowledge, threatened product liability, breach of
                  warranty or other claims, actions, arbitrations,
                  administrative or other proceedings regarding the Product or
                  the Trademarks, to which AHP is a party in the Territory; or
                  (ii) pending or, to AHP's knowledge, overtly threatened claim
                  against AHP asserting that any of the Know-How infringes or
                  violates the rights of Third Parties.

            (b)   AHP is the sole owner of the Trademarks, the Know-How and the
                  Regulatory Approvals for the Product in the Territory and AHP
                  has not sublicensed, pledged, encumbered, assigned,
                  transferred or granted any rights or interest therein to any
                  Third Party inconsistent with the rights granted to Horizon
                  under the Transaction Agreements, and prior to the Closing,
                  AHP will enter into no such agreement with any Affiliate or
                  Third Party.

            (c)   AHP has furnished Horizon with access to a complete copy of
                  the Regulatory Approvals, including all material amendments
                  and supplements thereto. To the best of AHP's knowledge, the
                  Regulatory Approvals are in good standing and nothing has come
                  to the attention of AHP which has, or reasonably should have,
                  led AHP to believe that the Regulatory Approvals are not in
                  good standing. To the best of AHP's knowledge, there is no
                  pending or overtly threatened action by the FDA which will
                  have a material adverse effect on the Regulatory Approvals.

            (d)   AHP represents and warrants that the list of Customer
                  Contracts provided herein is accurate and complete with
                  respect to current Customer Contracts and is, to the best of
                  AHP's knowledge, accurate and complete with respect to pending
                  Customer Contracts.

            (e)   AHP has not given any notice to any Third Parties asserting
                  misappropriation of trade secrets relating to the Know-How.

            (f)   EXCEPT AS OTHERWISE EXPRESSLY PROVIDED IN THIS AGREEMENT OR IN
                  THE PRODUCT SUPPLY AGREEMENT, AHP MAKES NO OTHER
                  REPRESENTATIONS OR WARRANTIES, EITHER EXPRESS OR IMPLIED,
                  INCLUDING, WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY
                  OR FITNESS FOR A PARTICULAR PURPOSE, WITH RESPECT TO THE
                  PRODUCTS OR THE TRADEMARKS OR HORIZON'S USE THEREOF.



                                       18
<PAGE>   19

      10.3  Representations and Warranties of Horizon. As of the signing of this
            Agreement, Horizon represents and warrants to AHP that it has
            properly determined that the net present value of the transactions
            contemplated by this Agreement is less than fifteen million dollars
            ($15,000,000) and no HSR filing is required in connection with the
            transactions contemplated hereby.

      10.4  Representation by Legal Counsel. Each Party hereto represents that
            it has been represented by legal counsel in connection with this
            Agreement and acknowledges that it has participated in the drafting
            hereof. In interpreting and applying the terms and provisions of
            this Agreement, the Parties agree that no presumption shall exist or
            be implied against the Party which drafted such terms and
            provisions.

11.   TERM AND TERMINATION.

      11.1  Term. This Agreement shall be effective as of the Effective Date
            and, unless terminated earlier by mutual written agreement of the
            Parties or pursuant to this Article 11, shall remain in full force
            and effect for so long as Horizon sells Product in the Territory
            (the "Term"). Notwithstanding the foregoing, upon the payment of all
            amounts due pursuant to Section 4.1 hereof the Know-How license
            granted to Horizon pursuant to Section 2.1.1 hereof shall become a
            fully paid-up, perpetual exclusive (exclusive except as to
            veterinary pharmaceutical products and injectable human uses by AHP
            and its Affiliates neither of which shall have the right to
            sublicense) license.

     11.2   Termination.

            11.2.1  Certifications of Representation and Warranties. Either
                    Party may terminate this Agreement if, in accordance with
                    Section 3.3.5 hereof, the other Party certifies that one or
                    more of its representations and warranties set forth in
                    Article 10 hereof do not remain true and in effect as of the
                    day of Closing.

            11.2.2  Termination for Cause Both Parties. This Agreement may be
                    terminated by written notice by either Party (subject to the
                    provisions of Section 11.2.3) at any time during the Term of
                    this Agreement:

               (a)  for material breach by the other Party, which breach remains
                    uncured for thirty (30) days in the case of nonpayment of




                                       19
<PAGE>   20

                  any amount due and ninety (90) days for all other breaches,
                  each measured from the date written notice of such breach is
                  given to the breaching Party, or, if such breach is not
                  susceptible of cure within such ninety (90) day period and the
                  breaching Party uses diligent good faith efforts to cure such
                  breach, for one hundred eighty (180) days after written notice
                  to the breaching Party; or

            (b)   upon the filing or institution of bankruptcy, reorganization,
                  liquidation or receivership proceedings, or upon an assignment
                  of a substantial portion of the assets for the benefit of
                  creditors by the other Party, or in the event a receiver or
                  custodian is appointed for such Party's business, or if a
                  substantial portion of such Party's business is subject to
                  attachment or similar process; provided, however, that in the
                  case of any involuntary bankruptcy proceeding such right to
                  terminate shall only become effective if the proceeding is not
                  dismissed within ninety (90) days after the filing thereof.

      11.2.3 Effect of Termination for Cause on License.

            (a)   In the event that Horizon breaches this Agreement pursuant to
                  Section 11.2.2 then it shall be AHP's sole option:

                  (i)   to terminate this Agreement, in which case all rights to
                        the Know-How, the Regulatory Approvals and the
                        Trademarks shall revert to AHP (unless all payments
                        under Section 4.1 have been fully paid to AHP) and
                        Horizon shall remain obligated to make all payments
                        under Sections 4.1 and 4.2 which have accrued as of the
                        date of termination; or

                  (ii)  to accelerate the payments required under Section 4.1 so
                        that they shall become immediately due and payable, in
                        which case this Agreement shall remain in full force and
                        effect, and Horizon shall remain obligated to make all
                        payments required under Sections 4.1 and 4.2; or

                  (iii) to pursue all legal and equitable remedies available to
                        it, in which case the Agreement shall remain in full
                        force and effect and Horizon shall remain obligated to
                        make all payments required under Sections 4.1 and 4.2.

               (b)  In the event that AHP breaches this Agreement pursuant to
                    Section 11.2.2 then it shall be Horizon's sole option:


                                       20
<PAGE>   21


                  (i)   to terminate this Agreement, in which case all rights to
                        the Know-How and the Regulatory Approvals shall be
                        vested in Horizon (if all payments under Section 4.1
                        have been fully paid to AHP) and the license under the
                        Trademarks shall be deemed to be fully paid-up and
                        Horizon shall remain obligated to make only those
                        payments under Section 4.2 which have accrued as of the
                        date of termination; or

                  (ii)  to pursue all legal and equitable remedies available to
                        it, in which case the Agreement shall remain in full
                        force and effect and Horizon shall remain obligated to
                        make all payments required under Sections 4.1 and 4.2.

            11.3  Survival. The provisions of Articles 1, 2, 6, 12 and 13 and
                  Sections 4.4, 4.5, 11.2.3, 14.2.3, 14.6, 14.7, 14.8, 14.9, and
                  14.10 shall survive expiration or any earlier termination of
                  this Agreement. Any payments that become due and payable prior
                  to expiration, which have not been paid, shall survive
                  expiration or any earlier termination of this Agreement.

12.   INDEMNIFICATION.

      12.1  Notice and Assistance. Each Party shall promptly notify the other,
            in writing, if it learns of any litigation, claim, administrative or
            criminal proceedings (collectively "Actions"), related to the
            Product, the Substance, the Trademark, or any Regulatory Approval,
            asserted or threatened against such Party (the "Defending Party").
            With respect to any Actions relating to the Product, the Substance,
            the Trademark or any Regulatory Approval asserted against a
            Defending Party, the other Party shall, at no out-of-pocket expense
            to it except as otherwise provided in this Article 12, reasonably
            cooperate with and provide such reasonable assistance to such
            Defending Party as such Defending Party may reasonably request in
            connection with its defense against such Actions. Such reasonable
            assistance may include, without limitation, providing copies of all
            relevant correspondence and other materials that the Defending Party
            may reasonably request, provided, however, that any Confidential
            Information so provided shall be treated in accordance with the
            provisions of Article 13 hereof.

      12.2  Indemnification by AHP. AHP shall indemnify, defend and hold
            harmless Horizon, its Affiliates or its permitted sublicensees, and
            each of its and their respective employees, officers, directors and
            agents (each, a "Horizon Indemnified Party") from and against any
            and all liability, loss, damage, cost, and expense (including
            reasonable attorneys' fees) (collectively, a "Liability") which the
            Horizon Indemnified Party may incur, suffer or be required to pay
            resulting from or arising in connection with (i) the breach by AHP
            of any representation or warranty contained in this Agreement, (ii)
            the manufacture, promotion,



                                       21
<PAGE>   22

            distribution, testing, use, marketing, sale or other disposition of
            the Substance or Products by AHP outside of the Territory and Field,
            whether before or after the Effective Date; (iii) the manufacture,
            promotion, distribution, testing, use, marketing, sale or other
            disposition of the Substance or Products by AHP within the Territory
            and Field before the Effective Date; or (iv) the use of the
            Trademarks by AHP or its Affiliates within or outside the Territory,
            whether before or after the Effective Date. Notwithstanding the
            foregoing, AHP shall have no obligation under this Agreement to
            indemnify, defend or hold harmless any Horizon Indemnified Party
            with respect to claims, demands, costs or judgments which result
            from willful misconduct or negligent acts or omissions of Horizon,
            its Affiliates, its permitted sublicensees, or any of their
            respective employees, officers, directors or agents.

      12.3  Indemnification by Horizon. Horizon shall indemnify, defend and hold
            harmless AHP and its Affiliates, and each of its and their
            respective employees, officers, directors and agents (each, an "AHP
            Indemnified Party") from and against any Liability which the AHP
            Indemnified Party may incur, suffer or be required to pay resulting
            from or arising in connection with (i) the breach by Horizon of any
            representation or warranty contained in this Agreement; (ii) the
            manufacture (but only upon the commencement of Horizon's
            manufacturing the Products pursuant to the Product Supply
            Agreement), promotion, distribution, testing, use, marketing, sale
            or other disposition of Products by Horizon, its Affiliates, its
            permitted sublicensees or their respective subcontractors; or (iii)
            the use of the Trademark by Horizon, its Affiliates, its permitted
            sublicensees or their respective subcontractors. Notwithstanding the
            foregoing, Horizon shall have no obligation under this Agreement to
            indemnify, defend, or hold harmless any AHP Indemnified Party with
            respect to claims, demands, costs or judgments which result from
            willful misconduct or negligent acts or omissions of AHP, its
            Affiliates, its permitted sublicensees or any of their respective
            employees, officers, directors or agents.

      12.4  Conditions to Indemnification. The obligations of the indemnifying
            Party under Sections 12.2 and 12.3 are conditioned upon the delivery
            of written notice to the indemnifying Party of any potential
            Liability promptly after the indemnified Party becomes aware of such
            potential Liability. The indemnifying Party shall have the right to
            assume the defense of any suit or claim related to the Liability if
            it has assumed responsibility for the suit or claim in writing;
            however, if in the reasonable judgment of the indemnified Party,
            such suit or claim involves an issue or matter which could have a
            materially adverse effect on the business operations or assets of
            the indemnified Party, the indemnified Party may waive its rights to
            indemnity under this Agreement and control the defense or settlement
            thereof, but in no event shall any such waiver be construed as a
            waiver of any indemnification rights such Party may have at law or
            in equity. If the indemnifying Party defends the suit or claim, the
            indemnified Party may participate in (but not control) the defense
            thereof at its sole cost and expense.



                                       22
<PAGE>   23

                    [***] - CONFIDENTIAL TREATMENT REQUESTED

      12.5  Settlements. Neither Party may settle a claim or action related to a
            Liability without the consent of the other Party, if such settlement
            would impose any monetary obligation on the other Party or require
            the other Party to submit to an injunction or otherwise limit the
            other Party's rights under this Agreement or otherwise. Except as
            otherwise expressly set forth in this Article 12, any payment made
            by a Party to settle any such claim or action shall be at its own
            cost and expense.

      12.6  Limitation of Liability. With respect to any claim by one Party
            against the other arising out of the performance or failure of
            performance of the other Party under this Agreement, the Parties
            expressly agree that the liability of such Party to the other Party
            for such breach shall be limited under this Agreement or otherwise
            at law or equity to direct damages only and in no event shall a
            Party be liable for punitive, exemplary or consequential damages.
            The limitations set forth in this Section 12.6 shall not apply with
            respect to the obligations of either Party to indemnify the other
            under Sections 12.2 or 12.3 hereof in connection with a Liability to
            a Third Party.

      12.7  Insurance. Horizon shall obtain and maintain at all times during the
            term of this Agreement, Commercial General Liability Insurance,
            including Products Liability Insurance, with reputable and
            financially secure insurance carriers to cover its indemnification
            obligations under Section 12.3, with limits of not less than [***]
            dollars ($[***]) per occurrence and [***] dollars ($[***]) in the
            aggregate. Horizon shall provide AHP with a Certificate of Insurance
            evidencing this coverage within thirty (30) days after the Closing.
            Such insurance policy shall name AHP as an additional insured and
            Horizon shall use its Commercially Reasonable Efforts to ensure that
            such insurance policy contains a provision requiring ten (10) day
            advance notification to AHP in the event of its cancellation or
            termination. AHP shall maintain self-insurance and/or obtain
            insurance from a Third Party insurer in amounts sufficient to cover
            its obligations under Section 12.2. Upon Horizon's written request,
            AHP shall provide Horizon with evidence of such insurance coverage.

13.  CONFIDENTIALITY.

      13.1  Nondisclosure Obligation. Each of Horizon and AHP shall use only in
            accordance with this Agreement and shall not disclose to any Third
            Party any information including, without limitation, Know-How,
            received by it from the other Party (the "Information"), without the
            prior written consent of the other Party. The foregoing obligations
            shall survive the expiration or earlier termination of the last of
            the Transaction Agreements to so expire or to be so terminated for a
            period of five (5) years. These obligations shall not apply to
            Information that:



                                       23
<PAGE>   24


            (i)   is known by the receiving Party at the time of its receipt,
                  and not through a prior disclosure by the disclosing Party, as
                  documented by business records;

            (ii)  is at the time of disclosure or thereafter becomes published
                  or otherwise part of the public domain without breach of this
                  Agreement by the receiving Party;

            (iii) is subsequently disclosed to the receiving Party by a Third
                  Party who has the right to make such disclosure;

            (iv)  is developed by the receiving Party independently of the
                  Information received from the disclosing Party and such
                  independent development can be documented by the receiving
                  Party, or

            (v)   is required by law, regulation, rule, act or order of any
                  governmental authority or agency to be disclosed by a Party,
                  provided that notice is promptly delivered to the other Party
                  in order to provide an opportunity to seek a protective order
                  or other similar order with respect to such Information and
                  thereafter the disclosing Party discloses to the requesting
                  entity only the minimum Information required to be disclosed
                  in order to comply with the request, whether or not a
                  protective order or other similar order is obtained by the
                  other Party.

      13.2  Permitted Disclosures. Information may be disclosed to employees,
            agents, consultants, sublicensees or suppliers of the recipient
            Party or its Affiliates, but only to the extent required to
            accomplish the purposes of this Agreement and only if the recipient
            Party obtains prior agreement from its employees, agents,
            consultants, sublicensees, suppliers or Third Party manufacturers to
            whom disclosure is to be made to hold in confidence and not make use
            of such Information for any purpose other than those permitted by
            this Agreement. Each Party will use at least the same standard of
            care as it uses to protect proprietary or confidential information
            of its own to ensure that such employees, agents, consultants,
            sublicensees, suppliers or Third Party manufacturers do not disclose
            or make any unauthorized use of the Information.

     13.3   Disclosure of Agreement. Neither Horizon nor AHP shall release to
            any Third Party or publish in any way any non-public information
            with respect to the terms of this Agreement or concerning their
            cooperation without the prior written consent of the other, which
            consent will not be unreasonably withheld or delayed, provided,
            however, that either



                                       24
<PAGE>   25

            Party may disclose the terms of this Agreement to the extent
            required to comply with applicable laws, including, without
            limitation the rules and regulations promulgated by the United
            States Securities and Exchange Commission, provided, however, that
            prior to making any such disclosure, the Party intending to so
            disclose the terms of this Agreement shall (i) provide the
            nondisclosing Party with written notice of the proposed disclosure
            and a opportunity to review and comment on the intended disclosure
            which is reasonable under the circumstances and (ii) shall seek
            confidential treatment for as much of the disclosure as is
            reasonable under the circumstances, including, without limitation,
            seeking confidential treatment of any information as may be
            requested by the other Party. Notwithstanding any other provision of
            this Agreement, each Party may disclose the terms of this Agreement
            to lenders, investment bankers and other financial institutions of
            its choice solely for purposes of financing the business operations
            of such Party either (i) upon the written consent of the other Party
            or (ii) if the disclosing Party uses reasonable efforts to obtain a
            signed confidentiality agreement with such financial institution
            with respect to such information on terms substantially similar to
            those contained in this Article 13.

      13.4  Publicity. Subject to Section 13.3, all publicity, press releases
            and other announcements relating to this Agreement or the
            transactions contemplated hereby shall be reviewed in advance by,
            and shall be subject to the approval of, both Parties.

14.   MISCELLANEOUS.

      14.1  Force Majeure. Neither Party shall be liable to the other for delay
            or failure in the performance of the obligations on its part
            contained in this Agreement if and to the extent that such failure
            or delay is due to circumstances beyond its control (including,
            without limitation, AHP's inability to obtain, from a Third Party,
            sufficient quantities of the raw materials needed for the
            manufacture of Substance to meet its manufacturing obligations under
            Article 7) which it could not have avoided by the exercise of
            reasonable diligence. It shall notify the other Party promptly
            should such circumstances arise, giving an indication of the likely
            extent and duration thereof and shall use all Commercially
            Reasonable Efforts to resume performance of its obligations as soon
            as practicable.

     14.2   Assignment.

            14.2.1 Assignment by Horizon. Horizon may assign any or all of its
                  rights or obligations under this Agreement in the Territory to
                  any of its Affiliates, for so long as they remain Affiliates.
                  In addition, Horizon may assign any or all of its rights or
                  obligations under this Agreement in the Territory in
                  conjunction


                                       25
<PAGE>   26

                  with a merger or acquisition of Horizon or its Affiliates.
                  Horizon may not otherwise assign any of its rights or
                  obligations under this Agreement without AHP's prior written
                  consent, not to be unreasonably withheld. AHP shall respond to
                  such requests by Horizon for assignment within thirty (30)
                  days from such request. Any permitted assignment shall not
                  relieve Horizon of its responsibilities for performance of its
                  obligations under this Agreement. Notwithstanding the
                  foregoing, Horizon may not assign or otherwise transfer the
                  Regulatory Approvals to any Third Party until the later to
                  occur of (i) all payments are made under Article 4.1, and (ii)
                  termination of the Product Supply Agreement.

            14.2.2 Assignment by AHP. AHP may assign any or all of its rights or
                  obligations under this Agreement to any of its Affiliates or
                  to any Third Party, provided, however, that AHP may assign all
                  or part of its obligations to a Third Party only after
                  receiving Horizon's prior written consent, which consent shall
                  not be unreasonably withheld or delayed; provided, further,
                  that such assignment shall not relieve AHP of its
                  responsibilities for performance of its obligations under this
                  Agreement. Notwithstanding the foregoing, Horizon's consent
                  shall not be required for any assignment made by AHP in
                  connection with a merger or similar reorganization of AHP or
                  its parent company or the sale of all or substantially all of
                  AHP's or AHP's parent company's pharmaceutical assets.

            14.2.3 Binding Nature of Assignment. This Agreement shall be binding
                  upon and inure to the benefit of the successors and permitted
                  assigns of the Parties. Any assignment not in accordance with
                  this Article 14 shall be void.

      14.3  No Waiver. The failure of either Party to require performance by the
            other Party of any of that other Party's obligations hereunder shall
            in no manner affect the right of such Party to enforce the same at a
            later time. No waiver by any Party hereto of any condition, or of
            the breach of any provision, term, representation or warranty
            contained in this Agreement whether by conduct or otherwise, in any
            one or more instances, shall be deemed to be or construed as a
            further or continuing waiver of any such condition or breach, or of
            any other condition or of the breach of any other provision, term,
            representation or warranty hereof.

      14.4  Severability. If a court or other tribunal of competent jurisdiction
            should hold any term or provision of this Agreement to be excessive,
            or invalid, void or unenforceable, the offending term or provision
            shall be deleted or revised to the extent necessary to be
            enforceable, and, if possible, replaced by a term or provision
            which, so far as practicable achieves the legitimate aims of the
            Parties.

      14.5  Relationship between the Parties. Both Parties are independent
            contractors under this Agreement. Nothing herein contained shall be
            deemed to create an employment, agency, joint venture or partnership
            relationship between the Parties hereto or any of their agents or


                                       26
<PAGE>   27

            employees, or any other legal arrangement that would impose
            liability upon one Party for the act or failure to act of the other
            Party. Neither Party shall have any express or implied power to
            enter into any contracts or commitments or to incur any liabilities
            in the name of, or on behalf of, the other Party, or to bind the
            other Party in any respect whatsoever.

      14.6  Correspondence and Notices.

          14.6.1 Ordinary Notices. Correspondence, reports, documentation, and
               any other communication in writing between the Parties in the
               course of ordinary implementation of this Agreement shall be
               delivered by hand, sent by facsimile, overnight courier or by
               airmail to the employee or representative of the other Party who
               is designated by such other Party to receive such written
               communication.

          14.6.2 Extraordinary Notices. Extraordinary notices and communications
               (including, without limitation, notices of termination, force
               majeure, material breach, change of address) shall be in writing
               and sent by prepaid registered or certified air mail, or by
               facsimile confirmed by prepaid registered or certified air mail
               letter, and shall be deemed to have been properly served to the
               addressee upon receipt of such written communication.

          14.6.3 Addresses. In the case of Horizon, the proper address for
               communications and for all payments shall be:

                                    Horizon Pharmaceutical Corporation
                                    660 Hembree Parkway, Suite 106
                                    Roswell, Georgia 30076
                                    Attn:  Mr. Brent Dixon
                                    Fax:  (770) 442-9594

               and it the case of AHP, the proper address for communications and
               for all payments shall be:

                                    Wyeth-Ayerst Laboratories
                                    555 Lancaster Avenue
                                    St. Davids, Pennsylvania 19087
                                    Attn:  Senior Vice President,
                                           Global Business Development
                                    Fax:  (610) 688-9498

                           with a copy to:

                                    American Home Products Corporation
                                    5 Giralda Farms
                                    Madison, New Jersey 07940
                                    Attn:  Senior Vice President
                                           and General Counsel
                                    Fax:  (973) 660-7156



                                       27
<PAGE>   28

      14.7  Choice of Law. This Agreement is subject to and governed by the laws
            of the State of Delaware, excluding its conflict of laws provisions.

      14.8  Entire Agreement Amendment. This Agreement, together with the other
            Transaction Agreements and the Confidential Disclosure Agreement
            between AHP and E.J. Financial Enterprises Inc. (an equity holder in
            Horizon) dated April 28, 1998, and all the covenants, promises,
            agreements, warranties, representations, conditions and
            understandings contained herein and therein sets forth the complete,
            full and exclusive agreement between the Parties and supersedes and
            terminates all prior and contemporaneous agreements and
            understandings between the Parties, whether oral or in writing.
            There are no covenants, promises, agreements, warranties,
            representations, conditions or understandings, either oral or
            written, between the Parties other than as are set forth in the
            Transaction Agreements. No subsequent alteration, amendment, change,
            waiver or addition to this Agreement shall be binding upon the
            Parties unless reduced to writing and signed by an authorized
            officer of each Party. No understanding, agreement, representation
            or promise, not explicitly set forth herein, has been relied on by
            either Party in deciding to execute this Agreement.

      14.9  Headings. The headings and captions used in this Agreement are
            solely for the convenience of reference and shall not affect its
            interpretation.

      14.10 Counterparts. This Agreement may be executed in one or more
            counterparts each of which shall be an original and all of which
            shall constitute together the same document.

      14.11 Further Actions. Each Party agrees to execute, acknowledge and
            deliver such further instruments, and to do all other acts, as may
            be necessary or appropriate in order to carry out the purposes and
            intent of this Agreement including, without limitation, any filings
            with any antitrust agency which may be required.


     IN WITNESS WHEREOF, this Agreement has been executed by the duly authorized
representatives of the Parties as of the date set forth below.

AMERICAN HOME PRODUCTS              HORIZON PHARMACEUTICALS, INC.
CORPORATION


-------------------------------     --------------------------------
Name:                               Name:
Title:                              Title:



                                       28
<PAGE>   29


                                    EXHIBIT A

                               CUSTOMER CONTRACTS
                               ------------------

         The Customer Contracts are listed on the following two pages.



                                       29
<PAGE>   30

                    [***] - CONFIDENTIAL TREATMENT REQUESTED
                            WYETH-AYERST LABORATORIES
                               BID ANALYSIS SYSTEM
                     CONTRACT PRODUCT PRICES BY NDC - ACTIVE

<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------- -------------------------------------------
NDC:  00031-7840-63 ROBINUL FORTE TABLETS                         PKG SIZE:  [***]
--------------------------------------------------------------------------------------- -------------------------------------------
CTLG PRICE:  [***]                FACTOR COST:  [***]                              FSS PRICE:  [***]
---------------------------------------------  --------------------------------------------------------------- --------------------
CURRENT BEST:  [***]              CURRENT NOMINALS:  [***]           FUTURE BEST:  [***]                   FUTURE NOMINAL:   [***]
---------------------------------------------------------------------------------------------------------------------- ------------

GRP/CUST       GRP/CUSTOMER NAME         CITY      STATE      CLS  CONTRACT     START DATE    END DATE      SALES     PRICE  DISC %
------------------------------------------------------------- ----------------- ------------ ------------ ----------- -----  -----
<S>            <C>                       <C>       <C>        <C>  <C>          <C>          <C>          <C>         <C>    <C>
01 - NON GUARANTEED TYPE
------------------------------------------------------------- ------------ -------------- ------------ ------------ -------- -----
000000489      PUERTO RICO HOSP GROUP     SAN JUAN       PR          0000046178   11/01/1997   11/30/1998            [***]  [***]
---------------- ----------------------------- ------------- ------------ -------------- ------------ ------------ -------- ------
791000010      HOSPITAL DEL MAESTRO       HATO REY       PR    14    0000046045   11/01/1997   11/30/1998            [***]  [***]
------------------------------------------------------------------- -------- -------------- ------------ ------------ -------- ---
02 - GUARANTEED
------------------------------------------------------------------- ------------   ---------- ------------ ------------ -------- ---
000000340      VETERANS STATE HOME        HINES          IL          0000046309    11/01/1998   11/30/1998           [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000000355      PHS FEDERAL GOVT ACCTS     WASHINGTON     DC          0000046308    11/01/1998   11/30/1998           [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000000406      MILITARY                   RADNOR         PA          0000046199    11/01/1998   11/30/1998   [***]   [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000000310      VA PRIME VENDOR            RADNOR         PA          0000046196    11/01/1998   11/30/1998   [***]   [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000002003      STATE OF ARKANSAS          LITTLE ROCK    AR          0000043007    01/01/1998   12/31/1998   [***]   [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000000027      MINNESOTA MULTI-STATE      ST. PAUL.      MN          0000046643    05/01/1998   04/30/1999   [***]   [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
0000009585     NEW PUERTO RICO HOSP       ST. DAVIDS     PA          0000047764    04/30/1998   04/27/1999           [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000000253      TENET HEALTCARE            DALLAS         TX          0000022284    09/01/1998   08/31/1999   [***]   [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000000309      HEALTH SERVS CORP AMER     BRIDGETON      MO          0000024878    10/01/1998   09/30/1999   [***]   [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
04 - GUARANTEED W/OUT - CLAUSE
---------------- ----------------------------- -------------- ------------ -------------- ------------ ------------ -------- -----
0000009341     MICH STATE UNIV AFFIL      EAST LANSING   MI           0000046646     02/01/1998   01/31/9999         [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
05 - GUAR W/PRC ESC & OUT CLS
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000000407      OWEN HEALTHCARE            HOUSTON        TX           0000031263     07/01/1998   03/31/2000 [***]   [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
000000418      PACT (G/MEDMGMNT)          PLYMOUTH       MN           0000046216     07/01/1998   03/31/2000         [***]  [***]
---------      ------------------------   ------------------------- ------------   ---------- ------------- ------- ------  ------
</TABLE>


                                       30
<PAGE>   31

                                        [***] - CONFIDENTIAL TREATMENT REQUESTED


                            WYETH-AYERST LABORATORIES
                               BID ANALYSIS SYSTEM
                     CONTRACT PRODUCT PRICES BY NDC - ACTIVE

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------- ------------------------------------------
NDC:  00031-7824-63 ROBINUL TABLETS                               PKG SIZE:  [***]
--------------------------------------------------------------------------------------- ------------------------------------------
CTLG PRICE:  [***]                   FACTOR COST:  [***]                           FSS PRICE:  [***]
--------------------------------------------- ----------------------------------------- ---------------------------------- -------
CURRENT BEST:  [***]                 CURRENT NOMINALS:  [***]           FUTURE BEST:  [***]         FUTURE NOMINAL:  [***]
--------------------------------------------- ----------------------------------------- ---------------------------------- -------

---------------- --------------------------------- ------------------ ---------- ------- --------------- ------------ ------------
GRP/CUST    GRP/CUSTOMER NAME          CITY       STATE  CLS CONTRACT    START DATE    END DATE       SALES    PRICE     DISC %
----------------------------------------------------------------------------------------------------------------------------------
<C>         <C>                        <C>        <C>    <C>             <C>           <C>            <C>      <C>       <C>
01 - NON-GUARANTEED TYPE
                                                      -----------------   ---------------   ------------   ------------ ----------
000000489   PUERTO RICO HOSP GROUP ..  SAN JUAN    PR       0000046178   11/01/1997    11/30/1998              [***]    [***]
----------   ------------------------  ------------   -----------------   ---------------   ------------   ------------ ----------
791000010   HOSPITAL DEL MAESTRO ....  HATO REY    PR   14  0000046045   11/01/1997    11/30/1998              [***]    [***]
----------   ------------------------  ------------   -----------------   ---------------   ------------   ------------ ---------
02 - GUARANTEED
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
 000000344   PHS                       BETHESDA    MD       0000058826   10/01/1998    12/31/1998     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
 000000340   VETERANS STATE HOME       HINES       IL       0000046309   01/01/1998    11/30/1998     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
 000000355   PYS FEDERAL GOVT ACCTS    WASHINGTON  DC       0000046308   01/01/1998    11/30/1998     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
 000000406   MILITARY                  RADNOR      PA       0000046199   01/01/1998    11/30/1998     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
 000000310   VA PRIME VENDOR           RADNOR      PA       0000046196   01/01/1998    11/30/1998     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
 000000164   ISD (INTERNAL SVCS DEPT)  LOS ANGELES CA       0000027546   02/01/1998    01/31/1999     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
 000000195   NEW YORK CITY HLTH & HOS  NEW YORK    NY       0000037145   09/15/1997    09/30/2000              [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
0000002003   STATE OF ARKANSAS         LITTLE ROCK AR       0000043007   01/01/1998    12/31/1998     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
0000000027   MINNESOTA MULTI-STATE     ST. PAUL    MN       0000046643   05/01/1998    04/30/1999     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
0000002046   STATE OF SOUTH CAROLINA   COLUMBIA    SC       0000046472   05/01/1998    04/30/1999     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
0000009585   NEW PUERTO RICO HOSP      ST. DAVIDS  PA       0000047764   04/30/1998    04/27/1999              [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
0000000253   TENET HEALTHCARE          DALLAS      TX       0000022284   09/01/1998    08/31/1999     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
0000000309   HEALTH SERVS CORP AMER    BRIDGETON   MO       0000024878   10/01/1998    09/30/1999     [***]    [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
0000002004   STATE OF CALIFORNIA       SACRAMENTO  CA       0000057964   10/05/1998    09/30/2000              [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
0000002048   STATE OF TENNESSEE        NASHVILLE   TN       0000060276   10/22/1998    07/31/1999              [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
04 - GUARANTEED W/OUT-CLAUSE
----------   ------------------------   ------------   ---------------   ------------  ------------   ------   ------   ------
0000009341   MICH STATE UNIV AFFIL     E.LANSING   MI       0000046646   02/01/98      01/31/99                [***]    [***]
----------   ------------------------  ------------   ---------------   ------------  ------------   ------   ------   ------
</TABLE>

                                       31
<PAGE>   32
                                        [***] - CONFIDENTIAL TREATMENT REQUESTED


<TABLE>
<CAPTION>
05 - GUAR W/PRC ESC & OUT CLS
<S>         <C>                         <C>              <C>     <C>      <C>           <C>          <C>      <C>      <C>
----------   ------------------------   ---------------  -------------    ------------  -----------  -------  ------   -------
GRP/CUST    GRP/CUSTOMER NAME           CITY      STATE  CLS  CONTRACT    START DATE    END DATE     SALES    PRICE    DISC %
-----------------------------------------------------------------------------------------------------------------------------
000000407   OWEN HEALTHCARE             HOUSTON   TX         0000031263   07/01/1998    03/31/2000   [***]    [***]    [***]
---------   --------------------------  -------------  ---------------   ------------- ------------   -------  ------- ------
000000418   PACT (C/MEDMGNT)            PLYMOUTH  MN         0000046216   07/01/1998    03/31/2000   [***]    [***]    [***]
---------   --------------------------  -------------  ---------------   ------------- ------------   -------  ------- ------
</TABLE>




                                       32
<PAGE>   33



                                    EXHIBIT B
                                    ---------

                                    PRODUCTS


<TABLE>
<CAPTION>
Country   NDC No.   Strength   Dosage Form   Package Size
-------   -------   --------   -----------   ------------
<S>       <C>       <C>        <C>           <C>
  USA     7824-63   1 mg       tablets       bottles of 100
  USA     7840-63   2 mg       tablets       bottles of 100
</TABLE>




                                       33
<PAGE>   34



                                    EXHIBIT C
                                    ---------

                                   TRADEMARKS


<TABLE>
<CAPTION>
Country             Trademark      Registration No.         Renewal Date
-------             ---------      ----------------         ------------
<S>                 <C>            <C>                      <C>
United States       Robinul        728,458                  03/13/2002
</TABLE>





                                       34
<PAGE>   35



                                    EXHIBIT D
                                    ---------

                              SYSTEMS TRANSFER PLAN


     Pursuant to Section 3.2 of that certain License Agreement entered into by
and between Horizon Pharmaceutical Corporation ("Horizon") and American Home
Products Corporation, acting through its Wyeth-Ayerst Laboratories Division
("AHP") on January 29, 1999 (the "License Agreement"), Horizon and AHP, by
signing below, each agree that the documents identified below and attached
hereto constitute the Systems Transfer Plan. Horizon and AHP each further agree
that to the extent any of the attached documents are inconsistent with the
License Agreement or the Product Supply Agreement which also was entered into by
Horizon and AHP on January 29, 1999, the terms and conditions of the License
Agreement or the Product Supply Agreement, as applicable, shall control. The
Parties recognize that this document serves as a guideline for the transition of
responsibilities for the Product from AHP to Horizon and that, to the extent
that this Systems Transfer Plan imposes timelines which are not expressly stated
within the License Agreement or the Product Supply Agreement, the failure to
strictly adhere to any such timelines set forth in this Systems Transfer Plan
shall not constitute a breach of either the License Agreement or the Product
Supply Agreement

     Attachments

          1.   Initial inventory shipment; Outstanding sales orders;
               Initial forecast; On-going purchase orders
          2.   Product/Quality Complaints
          3.   Labeling, Product Inserts, Tooling
          4.   Customer Contracts
          5.   Rebates
          6.   Manufacturing Plant Services
          7.   Regulatory
          8.   Returns
          9.   Chargebacks

HORIZON PHARMACUETICAL                 AMERICAN HOME PRODUCTS
  CORPORATION                          CORPORATION acting through its
                                       Wyeth-Ayerst Laboratories Division



By:_______________________________     By:__________________________________
Name:_____________________________     Name:________________________________
Title:____________________________     Title:_______________________________
Date:_____________________________     Date:________________________________




                                       35
<PAGE>   36



                  EXHIBIT E

           ADVERSE DRUG EVENT REPORTING PROCEDURE


   The Parties hereby agree that the following terms will govern disclosures
of each Party to the other with respect to adverse event reporting relating to
the Product or Substance as clinically tested or marketed by or on behalf of
either Party.

1.  Definitions.

   1.1 An Adverse Drug Experience ("ADE") is defined as:

     a) any experience which is adverse, including what are commonly
        described as adverse or undesirable experiences, adverse events,
        adverse reactions, side effects, or death due to any cause
        associated with, or observed in conjunction with the use of a
        drug, biological product, or device in humans, whether or not
        considered related to the use of that product:

        - occurring in the course of the use of a drug, biological
          product or device,

        - associated with, or observed in conjunction with product
          overdose, whether accidental or intentional

        - associated with, or observed in conjunction with product
          abuse, and/or

        - associated with, or observed in conjunction with product
          withdrawal.

     b) Any significant failure of expected pharmacological or biologic
        therapeutical action (with the exception of in clinical trials).

   1.2 Serious or Non-Serious is defined as:

       a)  A Serious ADE is any adverse drug experience occurring at any dose
           that results in any of the following outcomes: death, a
           life-threatening adverse  drug  experience, inpatient hospitalization
           or prolongation of existing hospitalization, a persistent or
           significant disability/incapacity, or a congenital anomaly/birth
           defect. Other important medical events that may not result in death,
           be life-threatening, or require hospitalization may be considered a
           serious adverse drug experience when, based upon appropriate medical
           judgment, they may jeopardize the patient or subject and may require
           medical or surgical intervention to prevent one of the outcomes
           listed in this definition. Examples of such medical events include
           allergic bronchospasm requiring intensive treatment in an emergency
           room or at home, blood dyscrasias or convulsions that do not result
           in inpatient hospitalization, or the development of drug dependency
           or drug abuse.



                                       36
<PAGE>   37


          b)   A Non-Serious ADE is any ADE which does not meet the criteria for
               a serious ADE.

     1.3  Life-threatening adverse drug experience is defined as any adverse
          drug experience that places the patient, in the view of the initial
          reporter, at immediate risk of death from the adverse drug experience
          as it occurred, i.e., it does not include an adverse drug experience
          that, had it occurred in a more severe form, might have caused death.

     1.4  Disability is defined as a substantial disruption of a person's
          ability to conduct normal life functions.

     1.5  An Unexpected ADE is defined as any ADE that is not listed in the
          current labeling for the drug product. This includes events that may
          be symptomatically and pathophysiologically related to an event listed
          in the labeling, but differ from the event because of greater severity
          or specificity.

     1.6  Associated with or related to the use of the drug is defined as: A
          reasonable possibility exists that the ADE was caused by the drug.

     1.7  NDA Holder is defined as: An "Applicant" as defined in 21 CFR Part
          314.3(b), for regulatory approval of a Product in any regulatory
          jurisdiction, including a holder of a foreign equivalent thereto.

     1.8  IND Holder is defined as: A "Sponsor" as defined in 21 CFR Part 313.1
          (b) of an investigational new drug in any regulatory jurisdiction,
          including a holder of a foreign equivalent thereto.

     1.9  Capitalized terms not defined in this Exhibit shall have the meaning
          assigned thereto in the Agreement.

2. With respect to the Product or Substance, the Parties agree as follows:

     a.   All initial reports and any follow-up information (oral or written)
          for any and all Serious ADEs as defined above (other than with respect
          to animal studies) which become known to either Party (other than from
          disclosure by or on behalf of the other Party) must be communicated by
          telephone, telefax or electronically directly to the other Party
          and/or the NDA Holder, IND Holder (individually and collectively
          referred to as "Holders") within forty-eight (48) hours of receipt of
          the information. Written confirmation of the Serious ADE received by
          such Party should be sent to the other Party and/or the Holders as
          soon as it becomes available, but in any event within forty-eight (48)
          hours of initial report of the Serious ADE by such Party.



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          b.   Both Parties shall exchange Medwatch and/or CIOMs forms and other
               health authority reports within forty-eight (48) hours of
               submission to any Regulatory Authority.

          c.   All initial reports and follow-up information received for all
               Non-Serious ADEs for marketed Product which become known to a
               Party (other than from disclosure by or on behalf of the other
               Party) must be communicated in writing, by telefax or
               electronically to the other Party within ten (10) days, on
               Medwatch or CIOMs forms (where possible).

          d.   Each Party shall coordinate and cooperate with the other whenever
               practicable to prepare a single written report regarding all
               Serious and/or Non-Serious ADEs, provided, however, that neither
               Party shall be obligated to delay reporting of any ADE in
               violation of applicable law or regulations regarding the
               reporting of ADEs.

3. The Parties further agree that:

          a.   A written report be forwarded to the other Party within
               forty-eight (48) hours of receipt by the Party making the report,
               for ADEs for animal studies which suggest a potential significant
               risk for humans;

          b.   Each Party will give the other Party a report via a print-out or
               computer disk of all ADEs reported to it and its Affiliates
               relating to the Product or Substance within the last year, within
               thirty (30) days of receipt of a request from the other Party but
               not more often than four (4) times a year;

          c.   If either Party wishes access to ADE Reports of the other Party
               relating to the Product or Substance, upon request of that Party,
               the other Party shall make available its ADE records relating to
               the Product or Substance (including computer disks) for viewing
               and copying by the other Party. The Parties may discuss the
               transfer of ADE Reports by computer disk.

          d.   Disclosure of information hereunder by a Party to the other Party
               shall continue as long as either Party and/or its Affiliates or
               designees continue to clinically test or market Product or
               Substance.

4.   Each Party shall diligently undertake the following further obligations
     where both Parties are or will be commercializing the Product or Substance
     pursuant to the Agreement and/or performing clinical trials with respect to
     the Product or Substance:



                                       38
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          a.   Upon the Effective Date, each Party shall identify individuals
               who shall be responsible for identifying all ADE reporting
               requirements in all countries of the Territory as set forth in
               the Agreement, and any amendments thereto;

          b.   To immediately consult with the other Party, with respect to the
               investigation and handling of any Serious ADE disclosed to it by
               the other Party or by a third Party and to allow the other Party
               to review the Serious ADE and to participate in the follow-up
               investigation;

          c.   To immediately advise the other Party of any Product and/or
               Substance safety communication received from a health authority
               and consult with the other Party with respect to any Product
               and/or Substance warning, labeling change or change to an
               investigators' brochure involving safety issues proposed by the
               other Party, including, but not limited to the safety issues
               agreed to by the Parties;

          d.   To diligently handle in a timely manner the follow-up
               investigation and resolution of each ADE reported to it;

          e.   To provide the other Party mutually agreed upon audit rights of
               its ADE reporting system and documentation, upon prior notice,
               during normal business hours, at the expense of the auditing
               Party and under the confidentiality obligations set forth in the
               Agreement;

          f.   To meet in a timely fashion from time to time as may be
               reasonably required to implement the adverse event reporting and
               consultation procedures  described in this Exhibit E, including
               identification of those individuals in each Party's Drug Safety
               group who will be responsible for reporting to and receiving ADE
               information from the other Party, and the development of a
               written standard operating procedure with respect to adverse
               event reporting responsibilities, including reporting
               responsibilities to investigators;

          g.   Where possible, to transmit all data electronically;

          h.   To report to each other any addenda, revisions or changes to the
               Agreement (e.g., change in territories, local regulations,
               addition of new licensors/licensees to the Agreement, etc.) which
               might alter the adverse event reporting responsibilities
               hereunder;

          i.   To utilize English as the language of communication and data
               exchange between the Parties;

          j.   To develop a system of exchange of documents and information in
               the event that the Agreement involves more than two Parties;

          k.   To work together to develop an electronic system to transmit ADE
               data.



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5.   The Parties may meet after the Effective Date of the Agreement to establish
     a separate agreement for adverse event exchange which will supersede this
     Exhibit E.