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                                                                   Exhibit 10.15

                              CONSULTING AGREEMENT

July 31, 1998
James G, Shook, Ph.D.
2237 Hopkins Avenue
Redwood City, CA 94062

Dear Jim,

1       Salix Pharmaceuticals, Inc., a California corporation (the "Company")
        wishes to obtain your services as a consultant on projects agreed by you
        and the Company in writing. The initial project on which you are to work
        is described on Exhibit A attached hereto. This letter shall constitute
        an agreement between you and the Company and contains all the terms and
        conditions relating to the services you are to provide.

2.      Either you or the Company may terminate this Agreement at any time by at
        least thirty (30) days prior written notice. Upon notice of termination
        by the Company, you will only perform those services specifically
        requested by the Company during such thirty day period. This Agreement
        will terminate automatically on the date six (6) months from the date
        hereof.

3.      As consideration for your services and other obligations you will be
        paid as set forth on Exhibit A attached hereto for work on the initial
        project. Fees for future projects will be set forth in the agreements
        concerning such projects.

4.      As additional consideration for your services hereunder, the Company
        will provide you with such support facilities and space as may be
        required in the Company's judgment to enable you to properly perform
        your services hereunder.

5.      You shall be reimbursed for reasonable travel and other out-of-pocket
        expenses incurred by you in connection with your services under this
        Agreement, provided that you provide receipts and obtain prior approval
        of the Executive Vice President of the Company for any significant
        expenses.

6.      Your relationship with the Company shall be that of an independent
        contractor and not that of an employee. You will not be eligible for any
        employee benefits, nor will the Company make deductions from payments
        made to you for taxes, which shall be your responsibility. You shall
        have no authority to enter into contracts, which bind the Company or
        create obligations on the part of the Company without the express prior
        authorization of the Company.


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7.      All services to be performed by you will be as agreed between you and
        the Executive Vice President of the Company. You shall be required to
        report to the Executive Vice President of the Company concerning your
        services performed under this Agreement. The nature and frequency of
        these reports will be left to the discretion of the Executive Vice
        President.

8.      You shall keep in confidence and shall not disclose or make available to
        third parties or make any use of any information or documents relating
        to your services under this Agreement or to the products, methods of
        manufacture, trade secrets, processes, business affairs or confidential
        or proprietary information of the Company (other than information in the
        public domain through no fault of your own, except with the prior
        written consent of the Company or to the extent necessary in performing
        tasks assigned to you by the Company. Upon termination of this Agreement
        you will return to the Company all documents, and other materials
        related to the services provided hereunder or furnished to you by the
        Company. Your obligations under this Paragraph 8 shall survive
        termination of this Agreement.

9.      You shall promptly disclose and hereby transfer and assign to the
        Company all right, title and interest to all techniques, methods,
        processes, formulae, improvements, inventions and discoveries made or
        conceived or reduced to practice by you, solely or jointly with others,
        in the course of providing services hereunder or with the use of
        materials or facilities of the Company during the period of this
        Agreement or which relate to the Company's business or its actual or
        demonstrably anticipated research or development (except as otherwise
        provided below). When requested by the Company you will make available
        to the Company all notes, drawings, data and other information relating
        to the above. You will promptly sign any documents (including U.S. and
        foreign patent assignments) requested by the Company related to the
        above assignment of rights and inventions and will cooperate with the
        prosecution of any U.S. or foreign patent applications related to such
        rights and inventions. Your obligations under this Paragraph 9 shall
        survive termination of this Agreement. This Agreement does not apply to
        inventions covered by Section 2870 of the California Labor Code, a copy
        of which is attached hereto as Exhibit C, or to inventions which were
        made prior to the date of this Agreement and which are listed on Exhibit
        B attached hereto (if any).

10.     Any amendment to this Agreement must in writing signed by you and the
        Company.

11.     All notices, requests and other communications called for by this
        Agreement shall be deemed to have been given if made in writing and
        mailed, postage prepaid, if to you at the address set forth above and if
        to the Company at 3600 W. Bayshore Drive, Suite 205, Palo Alto,
        California 94303, or to such other addresses as either party shall
        specify to the other.


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12.     The validity, performance and construction of this Agreement shall be
        governed by the laws of the State of California.

13.     This Agreement supersedes any prior consulting or other agreements
        between you and the Company.

IF THIS AGREEMENT IS SATISFACTORY, YOU SHOULD EXECUTE AND RETURN THE ORIGINAL
AND RETAIN THE SECOND COPY FOR YOUR FILE.

Dated as of: July 27, 1998

                                Very truly yours,

                                SALIX PHARMACEUTICALS, INC.

                                By:     /s/ David Boyle
                                        -------------------------------
                                        David Boyle
                                Title:  Executive Vice President

AGREED AND ACCEPTED:

/s/ JAMES G. SHOOK
- -------------------------------
James G. Shook, Ph.D.


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                                    EXHIBIT A

DESCRIPTION OF INITIAL CONSULTING PROJECT AND COMPENSATION

        Salix Pharmaceuticals, Inc. (the "Company") wishes to enlist the
consulting services of James G. Shook. Ph.D. Initial work will consist of the
following description:

1)      Provide strategic, operational and regulatory advice on the Colazide
        project. Attend project review meetings at Salix, participate in FDA
        conference calls and visits to the FDA as requested.

2)      Review written documents and answer questions from the Colazide project
        team. Respond to requests by phone, FAX and email.

3)      Respond to questions, provide advice, review documents and development
        plans for rifaximin as requested. If needed, attend project team
        meetings at Salix.

Compensation for consulting services rendered under this Agreement will be:

        $175.00/hour (Retainer of 8 hours per week)

        $175.00/hour (Additional hours beyond 8 hours/week)

        Payment will be made upon receipt of invoice for consulting services.

        Invoices for travel and other expenses will be submitted with original
        receipts.


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                                    EXHIBIT B

INVENTIONS MADE PRIOR TO THIS AGREEMENT AND EXCLUDED FROM PARAGRAPH 9 (IF NONE,
SO STATE):


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                                    EXHIBIT C

Section 2870 of the California Labor Code is as follows:

(a)     Any provision in an employment agreement which provides that an employee
        shall assign, or offer to assign, any of his or her rights in an
        invention to his or her employer shall not apply to an invention that
        the employee developed entirely on his or her own time without using the
        employer's equipment, supplies, facilities or trade secret information
        except for those inventions that either:

        (1)     Relate at the time of conception or reduction to practice of the
                invention to the employer's business, or actual or demonstrably
                anticipated research or development of the employer.

        (2)     Result from any work performed by the employee for the employer.

(b)     To the extent a provision in an employment agreement purports to require
        an employee to assign an invention otherwise excluded from being
        required to be assigned under subdivision (a), the provision is against
        the public policy of this state and is unenforceable.