<PAGE>
                                                                   Exhibit 10.13

                                WAIVER AGREEMENT

     This WAIVER AGREEMENT (this "AGREEMENT") is entered into by and between
Richard J. Havens ("EXECUTIVE") and Medicis Pharmaceutical Corporation (the
"COMPANY"), effective as of July 15, 2005.

     WHEREAS, the Company has entered into that certain Agreement and Plan of
Merger, dated as of March 20, 2005 (the "MERGER AGREEMENT"), by and among
Medicis, Masterpiece Acquisition Corp., a Delaware corporation and wholly-owned
subsidiary of Medicis, and Inamed Corporation ("INAMED");

     WHEREAS, pursuant to the terms and subject to the conditions of the Merger
Agreement, Inamed would be merged with and into a wholly-owned subsidiary of the
Company (the "MERGER") and the separate corporate existence of Inamed would
thereafter cease to exist;

     WHEREAS, Executive holds (i) one or more options to purchase shares of the
Company's common stock, as those options are more particularly identified on
attached Schedule I (all such identified options, together with any other of
Executive's currently outstanding options or rights to purchase the Company's
capital stock, collectively, the "OPTIONS") and (ii) the number of currently
unvested shares of the Company's common stock listed on attached Schedule II
(all such listed unvested shares, together with any other currently outstanding
unvested shares of the Company's capital stock which have been issued to
Executive, collectively, the "RESTRICTED STOCK");

     WHEREAS, under the provisions of the applicable documents governing the
Options and the shares of Restricted Stock between Executive and the Company, as
currently in effect, each of the Options will vest and become exercisable in
full, and each of the shares of Restricted Stock will vest in full, on an
accelerated basis upon stockholder approval of a transaction that would
constitute a "Change of Control" (as such term is defined in the applicable
governing documents) (the "MERGER ACCELERATION BENEFITS");

     WHEREAS, the Company desires that Executive agree to waive any and all
rights to receive the Merger Acceleration Benefits in connection with the
stockholder approval of the proposed Merger, the consummation of the proposed
Merger, or the consummation of any other transaction(s) in connection with the
proposed Merger; and

     WHEREAS, in exchange for Executive's agreement to waive his right to
receive the Merger Acceleration Benefits, the Company agrees that (i) each of
the Options and each of the Restricted Shares shall vest in full on an
accelerated basis in the event of Executive's death or Disability (as defined
below) at any time following the consummation of the proposed Merger or in the
event of Executive's "Involuntary Termination" (as defined below) during the
24-month period following the consummation of the proposed Merger (the
"SUBSEQUENT MERGER ACCELERATION BENEFITS") and (ii) Executive shall be entitled
to receive a lump sum cash payment equal to $50,000 upon consummation of the
proposed Merger, subject to reduction for all applicable payroll and withholding
taxes.

<PAGE>

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Company and Executive hereby
agree as follows:

     1. Notwithstanding anything to the contrary contained in any document
governing the Options, the Restricted Stock, or the Merger Acceleration
Benefits, Executive hereby waives any and all of Executive's right or
entitlement to receive the Merger Acceleration Benefits in connection with the
stockholder approval of the proposed Merger, the consummation of the proposed
Merger, or the consummation of any other transaction(s) in connection with the
proposed Merger, but only the proposed Merger.

     2. Executive shall be entitled to receive a lump sum cash payment of
$50,000 no later than 15 days following the consummation of the proposed Merger,
subject to reduction for all applicable payroll and withholding taxes.

     3. In the event of Executive's death or Disability (as defined in Section 5
below) at any time following the consummation of the proposed Merger, or in the
event of Executive's Involuntary Termination (as defined in Section 5 below)
during the 24-month period following the consummation of the proposed Merger,
Executive shall be entitled to receive the Subsequent Merger Acceleration
Benefits.

     4. In no event shall Executive be entitled to receive the cash payment or
the Subsequent Merger Acceleration Benefits in the event the proposed Merger is
not consummated.

     5. For purposes of this Agreement, the following definitions shall be in
effect:

          (i) An "INVOLUNTARY TERMINATION" shall mean the termination of
Executive's employment or service by reason of:

               (A) Executive's involuntary dismissal or discharge by the Company
(or any affiliate of the Company) for reasons other than "Cause," or

               (B) Executive's voluntary resignation for "Good Reason."

          (ii) "CAUSE" shall mean Executive's (a) willful and continued failure
to substantially perform the duties of the Company (other than a failure
resulting from the Executive's disability), (b) willful engaging in conduct
which is demonstrably injurious to the Company or any subsidiary, monetarily or
otherwise, (c) conviction of a felony, or (d) significant violation of any
statutory or common law duty of loyally to the Company. The foregoing definition
shall not in any way preclude or restrict the right of the Company (or any
affiliate of the Company) to discharge or dismiss Executive or any other person
in the employ or service of the Company (or any affiliate of the Company) for
any other acts or omissions, but such other acts or omissions shall not be
deemed, for purposes of the this Agreement, to constitute grounds for
termination for Cause.

          (iii) Executive shall have "GOOD REASON" to terminate employment with
the Company when (a) Executive's duties, responsibilities or authority are
materially reduced or diminished without the Executive's prior written consent,
(b) Executive's compensation or benefits are reduced from the compensation and
benefits which exist for Executive on the effective date of the proposed Merger
(other than ordinary course diminutions in potential bonuses based on
performance), (c) the Company reduces the potential earnings of Executive under
any performance based bonus or incentive plan of the Company in effect
immediately prior


                                       2

<PAGE>

to the effective date of a proposed Merger which is disproportionate as compared
to other executives employed by the Company or any newly created organization of
which the Company may become a part, (d) the Company amends or terminates any
performance-based bonus or incentive plan of the Company in effect immediately
prior to the effective date of the proposed Merger or (e) the Company requires
Executive's principal place of employment to be greater than 25 miles from
Executive's principal place of employment on the date of the proposed Merger.

          (iv) "DISABILITY" shall mean the inability of Executive to engage in
any substantial gainful activity by reason of any medically determinable
physical or mental impairment which is expected to result in death or has lasted
or can be expected to last for a continuous period of not less than twelve (12)
months.

     6. This Agreement shall apply only with respect to Executive's right to
receive the Merger Acceleration Benefits in connection with the proposed Merger.

     7. This Agreement shall not in any way affect any benefits to which
Executive may become entitled in connection with the Company's Amended and
Restated Executive Retention Plan.

     8. Except as expressly modified by this Agreement, all other terms and
conditions applicable to the Options and the Restricted Stock shall remain in
full force and effect.

     9. This Agreement shall be administered, interpreted, and enforced under
the internal laws of the State of Arizona without regard to the principles of
conflicts of laws thereof.

     IN WITNESS WHEREOF, the undersigned have executed this Waiver Agreement to
be effective as of the date first written above.

                                        MEDICIS PHARMACEUTICAL CORPORATION


                                        By: /s/ Mark A. Prygocki, Sr.
                                            ------------------------------------
                                        Its:
                                             -----------------------------------


                                        EXECUTIVE


                                        /s/ R J. Havens
                                        ----------------------------------------
                                        (Signature)

                                        R J. Havens
                                        ----------------------------------------
                                        (Print Name)

                                        7/20/05


                                       3

<PAGE>

                                   SCHEDULE I

                                 LIST OF OPTIONS

<TABLE>
<CAPTION>
                                                  TOTAL NUMBER OF
                 EXERCISE   TOTAL NUMBER OF   UNVESTED OPTION SHARES
                PRICE PER    OPTION SHARES       (DETERMINED AS OF
  GRANT DATE      SHARE         GRANTED           APRIL 29, 2005)
  ----------    ---------   ---------------   ----------------------
<S>             <C>         <C>               <C>
July 16, 2004     $38.45         63,000               63,000
July 31, 2003     $29.20         59,576               53,276
July 31, 2003     $29.20          3,424                3,424
July 11, 2002     $18.33         57,544               44,944
July 11, 2002     $18.33          5,456                5,456
July 17, 2001     $26.95         59,290               34,090
July 17, 2001     $26.95          3,710                3,710
July 25, 2000     $27.63         86,382               14,382
July 25, 2000     $27.63          3,618                3,618
</TABLE>

<PAGE>

                                   SCHEDULE II

                            LIST OF RESTRICTED STOCK

<TABLE>
<CAPTION>
                                  TOTAL UNVESTED SHARES OF
                TOTAL SHARES OF       RESTRICTED STOCK
                   RESTRICTED         (DETERMINED AS OF
  GRANT DATE      STOCK ISSUED         APRIL 29, 2005)
  ----------    ---------------   ------------------------
<S>             <C>               <C>
July 24, 2001        20,000                16,000
</TABLE>