<PAGE>
                                                                   Exhibit 10.72


                                 April 21, 1998



Lawrence T. Friedhoff, M.D., Ph.D.
525 River Vale Road
River Vale, New Jersey  07675

Dear Dr. Friedhoff:

         I am very pleased to offer you a position at Aura Laboratories, Inc.
("Aura"), a subsidiary of Andrx Corporation ("Andrx"), upon the following terms:

(1)     Position:          Executive Vice President R&D, supervising the
                           preclinical and clinical operations of Aura and
                           performing such other duties as may be delegated to
                           you by Andrx.

(2)     Reporting To:      Eliot F. Hahn, Ph.D., President

(3)     Salary:            $255,000 annually

(4)     Stock              Options: 20,000 shares of Andrx common stock.
                           Although the actual stock option grant, vesting
                           schedule and exercise price of those options will be
                           determined by the Compensation Committee of the Board
                           of Directors of Andrx Corporation, we anticipate that
                           these options will vest in equal annual increments of
                           5,000 shares over a four-year period of time.
                           Additional options will be periodically granted based
                           upon your performance and the performance of your
                           work group.

(5)     Office:            To be determined, but your immediate work group will
                           be based in the Northern Bergen County, New Jersey
                           area.

(6)     Benefits:          Andrx maintains a 401(k) plan and makes a "matching"
                           contribution of 50% of the amount you contribute to
                           the plan, up to 5% of your annual compensation and
                           applicable laws. Andrx also maintains group medical,
                           dental and life insurance plans for all of its
                           full-time employees and their families. Andrx will
                           secure alternative medical benefits (an indemnity
                           medical insurance policy and will pay for your COBRA
                           benefits until that policy is in place) for you and
                           the other employees in the New Jersey office, and
                           will include those employees in its other benefit
                           plans, such as its 401(k) plan. If you are concerned
                           that any particular benefit is unavailable to you
                           through Andrx, we will work with you to resolve that
                           problem.



<PAGE>
Lawrence T. Friedhoff, M.D., Ph.D.
April 21, 1998
Page 2


(7)     Expenses:          Aura will pay or reimburse you for all reasonable
                           travel, educational, entertainment and other expenses
                           which you incur in connection with the performance of
                           your duties, provided such expenses are appropriately
                           documented and are within the budget Aura establishes
                           for you and your office.

(8)     Report             Date: As soon as possible.

(9)     Other              Activities: Aura will allow you to engage in such
                           other business activities as you desire including,
                           but not limited to, those specifically set forth in
                           subparagraphs "A-D" hereof, provided such activities
                           do not (i) conflict with any activities which Andrx
                           then engages in or, prior to your request,
                           contemplates engaging in or (ii) detract from the
                           time and quality of work you are expected to perform
                           for Andrx. Prior to engaging in any such other
                           activity, you will be expected to disclose, in
                           writing, the general nature of the activity which you
                           seek to engage in and the time commitment which you
                           envision for such endeavor. If reasonably acceptable
                           to Aura under the terms outlined above, Aura will
                           issue a written acceptance permitting you to perform
                           that outside activity on the terms specified or on
                           such other terms we may agree upon. Any intellectual
                           property rights derived from permitted outside
                           activities will belong to you, rather than to Aura.
                           Andrx recognizes that this right to engage in "Other
                           Activities" represents a significant consideration in
                           your decision to accept this offer and that in doing
                           so, you are relying on Andrx's representation that it
                           will make good faith efforts to implement this
                           paragraph.

         Pursuant to the foregoing, at this time Aura permits you to continue
the following categories of projects, previously disclosed by you:

         A.    Discover, development and/or commercialization of new chemical
               entities and/or natural products which you commenced working on
               prior to your employment.

         B.    Discover, development and/or commercialization of combinations of
               currently marketed products which you commenced working on prior
               to your employment.

         C.    Development activities rendered on a PRO BONO basis.

         D.    Teaching and/or academic activities.

         Aura's acceptance of A and B above is based on your representation that
those activities do not conflict with Aura's plans, as discussed with you. Aura
acknowledges that the foregoing activities will entail a time commitment from
you of approximately eight (8) hours per week.
<PAGE>

Lawrence T. Friedhoff, M.D., Ph.D.
April 21, 1998
Page 3


         This offer of employment assumes that you employment by Aura and the
performance of your duties will not violate the terms of any non-compete or
other agreements to which you are a party. Moreover, as your position will give
you access to information which Andrx keeps confidential, your execution of a
Confidentiality and Non-Competition Agreement will be a condition of your
employment.

         I am sure that you will find the environment here at Andrx both
stimulating and rewarding and we look forward to your joining us. Should you
have any questions, please feel free to call me.

         Please signify your acceptance of this offer by signing a copy of this
letter where indicated below and returning that copy to me by either fax (at
954-792-1034) or by mail as soon as possible.

                                              Sincerely,


                                              /s/ Elliot F. Hahn
                                              -----------------------------
                                              Elliot F. Hahn, Ph.D.
                                              President

AGREED TO AND ACCEPTED ON
THIS 13TH DAY OF MAY, 1998


/s/ Lawrence T. Friedhoff
-------------------------
Lawrence T. Friedhoff, M.D., Ph.D.


cc:      Chih-Ming Chen, Ph.D.
         Alan Cohen
         Scott Lodin