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                                                                    EXHIBIT 99.1

                                 CERTIFICATIONS

      On May 15, 2003, Questcor Pharmaceuticals, Inc. filed its Quarterly Report
on Form 10-Q for the quarter ended March 31, 2003 (the "Form 10-Q") with the
Securities and Exchange Commission. Pursuant to 18 U.S.C. Section 1350, as
created by Section 906 of the Sarbanes-Oxley Act of 2002, the following
certifications are being made to accompany the Form 10-Q:

                    CERTIFICATION OF CHIEF EXECUTIVE OFFICER

      Pursuant to 18 U.S.C. Section 1350, as created by Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned officer of Questcor Pharmaceuticals,
Inc. (the "Company") hereby certifies, to such officer's knowledge, that:

(i) the Quarterly Report on Form 10-Q of the Company for the quarter ended March
31, 2003 (the "Report") fully complies with the requirements of Section 13(a) or
Section 15(d), as applicable, of the Securities Exchange Act of 1934, as
amended; and

(ii) the information contained in the Report fairly presents, in all material
respects, the financial condition and results of operations of the Company.

Dated: May 15, 2003                                   /s/ Charles J. Casamento
                                                      --------------------------
                                                      Charles J. Casamento
                                                      Chief Executive Officer

The foregoing certification is being furnished solely to accompany the Report
pursuant to 18 U.S.C. Section 1350, and is not being filed for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be
incorporated by reference into any filing of the Company, whether made before or
after the date hereof, regardless of any general incorporation language in such
filing.

                    CERTIFICATION OF CHIEF FINANCIAL OFFICER

      Pursuant to 18 U.S.C. Section 1350, as created by Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned officer of Questcor Pharmaceuticals,
Inc. (the "Company") hereby certifies, to such officer's knowledge, that:

(i) the Quarterly Report on Form 10-Q of the Company for the quarter ended March
31, 2003 (the "Report") fully complies with the requirements of Section 13(a) or
Section 15(d), as applicable, of the Securities Exchange Act of 1934, as
amended; and

(ii) the information contained in the Report fairly presents, in all material
respects, the financial condition and results of operations of the Company.

Dated: May 15, 2003                                   /s/ Timothy E. Morris
                                                      --------------------------
                                                      Timothy E. Morris
                                                      Chief Financial Officer

The foregoing certification is being furnished solely to accompany the Report
pursuant to 18 U.S.C. Section 1350, and is not being filed for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be
incorporated by reference into any filing of the Company, whether made before or
after the date hereof, regardless of any general incorporation language in such
filing.