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| x | ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

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| o | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

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| California                                                    |   | 33-0476164 |
| (State or other jurisdiction ofincorporation or organization) |   | (I.R.S. EmployerIdentification No.) |
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| 1300 North Kellogg Drive, Suite DAnaheim, California          |   | 92807 |
| (Address of principal executive offices)                      |   | (Zip Code) |

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| Title of Each Class        |   | Name of Each Exchange on Which Registered |
| Common Stock, no par value |   | Nasdaq Stock Market, LLC                                            (Nasdaq Global Select Market) |

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| x  Large accelerated filer |   | o  Accelerated filer |    | o  Non-accelerated filer |   | o  Smaller reporting company |
|                                 |   | (Do not check if a smaller reporting company) |

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Table of Contents

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| QUESTCOR PHARMACEUTICALS, INC. |
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| By                             |   | /s/ Don M. Bailey |
|                           |   | Don M. BaileyPresident and Chief Executive Officer |

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|      |    | Description |
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| 2.1(1)    |    | Merger agreement entered into August 4, 1999, by and among Cyprus Pharmaceutical Corporation, a California corporation (“Parent”), Cyprus Acquisition Corporation, a Delaware corporation and a wholly owned subsidiary of Parent, and RiboGene, Inc., a Delaware corporation. |
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| 3.1(2)    |    | Amended and Restated Articles of Incorporation of the Company. |
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| 3.5(21)   |    | Amended and Restated Bylaws of Questcor Pharmaceuticals, Inc, dated as of October 20, 2009. |
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| 10.1(3)   |    | Forms of Incentive Stock Option and Non-statutory Stock Option. |
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| 10.2(4)   |    | 1992 Employee Stock Option Plan, as amended.** |
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| 10.3(5)   |    | 1993 Non-employee Directors’ Equity Incentive Plan, as amended and related form of Nonstatutory Stock Option.** |
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| 10.5(6)   |    | Asset Purchase Agreement dated July 27, 2001 between the Company and Aventis Pharmaceuticals Products, Inc.† |
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| 10.6(6)   |    | First Amendment to Asset Purchase Agreement dated January 29, 2002, between the Company and Aventis Pharmaceuticals Products, Inc.† |
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| 10.27(7)  |    | 2004 Non-Employee Directors’ Equity Incentive Plan.** |
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| 10.30(8)  |    | Letter Agreement between the Company and Steve Cartt dated March 7, 2005.** |
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| 10.31(8)  |    | Letter Agreement between the Company and Steve Cartt dated March 8, 2005.** |
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| 10.40(9)  |    | Asset Purchase Agreement dated October 17, 2005 by and between Questcor Pharmaceuticals, Inc. and QOL Medical LLC. |
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| 10.45(11) |    | Amended and Restated 2006 Equity Incentive Award Plan.** |
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| 10.46(12) |    | Form of Incentive Stock Option Agreement under the 2006 Equity Incentive Award Plan. |
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| 10.47(12) |    | Form of Non-Qualified Stock Option Agreement under the 2006 Equity Incentive Award Plan. |
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| 10.48(12) |    | Form of Restricted Stock Award Agreement under the 2006 Equity Incentive Award Plan. |
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| 10.58(13) |    | Amended Change of Control Letter Agreement between the Company and Stephen L. Cartt dated February 13, 2007.** |
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| 10.63(13) |    | Change of Control Letter Agreement between the Company and David J. Medeiros dated February 13, 2007.** |
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| 10.65(14) |    | Form of Performance-Based Vesting Stock Option Agreement under the 2006 Equity Incentive Award Plan. |
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| 10.66(15) |    | Severance Agreement between the Company and David J. Medeiros dated July 16, 2007.** |

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| 10.68(16) |    | Form of Option Agreement under the 2004 Non-Employee Directors’ Equity Incentive Plan for Director Options. |
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| 10.69(16) |    | Form of Option Agreement under the 2004 Non-Employee Directors’ Equity Incentive Plan for Committee Options. |
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| 10.70(17) |    | Amended and Restated 2003 Employee Stock Purchase Plan.** |

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| 10.77(20)  |    | Amended and Restated Employment Agreement between the Company and Don Bailey dated December 19, 2008.** |
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| 10.78(20)  |    | Form of 409A Letter Amendment to Officers’ Severance, Change in Control and Employment Agreements.** |
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| 10.81(21)  |    | Offer Letter, by and between Questcor Pharmaceuticals, Inc. and Dr. David Young, Pharm.D., Ph.D., dated October 15, 2009.** |
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| 10.82(21)  |    | Severance Agreement, by and between Questcor Pharmaceuticals, Inc. and Dr. David Young, Pharm.D., Ph.D., dated October 19, 2009.** |
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| 10.83(22)  |    | Supply Agreement, dated January 21, 2010, by and between Questcor Pharmaceuticals, Inc. and Cangene bioPharma, Inc.† |
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| 10.86(23)  |    | Offer Letter, dated January 3, 2011, by and between Questcor Pharmaceuticals, Inc. and Michael Mulroy.** |
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| 10.87(23)  |    | Severance Agreement, dated January 3, 2011, by and between Questcor Pharmaceuticals, Inc. and Michael Mulroy.** |
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| 10.88(24)  |   | Supply Agreement, dated July 14, 2010, by and between Questcor Pharmaceuticals, Inc. and BioVectra, Inc. † |
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| 10.89*(25) |    | Share Purchase Agreement, dated January 2, 2013, by and among the Vendors, BioVectra Inc., Questcor Pharmaceuticals, Inc., 101610 P.E.I. Inc., and Vendors' Representative. † |
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| 21.1(26)   |   | Subsidiaries of Registrant. |
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| 23.1*      |    | Consent of OUM & Co. LLP, Independent Registered Public Accounting Firm. |
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| 23.2(26)   |   | Consent of BDO USA, LLC, Independent Registered Public Accounting Firm. |
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| 31.1(26)   |    | Certification of Chief Executive Officer Pursuant to Rule 13a-14(a)/15d-14(a) of the Securities Exchange Act of 1934. |
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| 31.2(26)   |    | Certification of Chief Financial Officer Pursuant to Rule 13a-14(a)/15d-14(a) of the Securities Exchange Act of 1934. |
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| 32.1(26)   |    | Certification of Chief Executive Officer Pursuant to Rule 13a-14(b)/15d-14(b) of the Securities Exchange Act of 1934 and 18 U.S.C. Section 1350. (3) |
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| 32.2(26)   |    | Certification of Chief Financial Officer Pursuant to Rule 13a-14(b)/15d-14(b) of the Securities Exchange Act of 1934 and 18 U.S.C. Section 1350. (3) |

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| 101.INS*** |   | XBRL Instance Document |
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| 101.SCH*** |   | XBRL Taxonomy Extension Schema Document |
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| 101.CAL*** |   | XBRL Taxonomy Extension Calculation Linkbase Document |
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| 101.DEF*** |   | XBRL Taxonomy Extension Definition Linkbase Document |
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| 101.LAB*** |   | XBRL Taxonomy Extension Label Linkbase Document |
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| 101.PRE*** |   | XBRL Taxonomy Extension Presentation Linkbase Document |

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| * | Filed herewith. |

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| ** | This exhibit is identified as a management contract or compensatory plan or arrangement pursuant to Item 15(a)(3) of Form 10-K. |

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| *** | XBRL information is furnished and not filed or a part of a registration statement or prospectus for purposes of section 11 or 12 of the Securities Act of 1933, as amended, is deemed not filed for purposes of section 18 of the Securities Exchange Act of 1934, as amended, and otherwise is not subject to liability under these section. |

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| (1) | Filed as an exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 1999, filed on March 30, 2000, and incorporated herein by reference. |

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| (2) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on March 27, 2008, and incorporated herein by reference. |

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| (3) | Filed as an exhibit to the Company’s Registration Statement on Form S-1, Registration No. 33-51682, and incorporated herein by reference. |

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| (4) | Filed as an exhibit to the Company’s Proxy Statement on Schedule 14A, filed on March 28, 2002, and incorporated herein by reference. |

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| (5) | Filed as an exhibit to the Company’s Registration Statement Form S-4, Registration Statement No. 333-87611, filed on September 23, 1999, and incorporated herein by reference. |

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| (6) | Filed as an exhibit to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2002, filed on August 14, 2002, and incorporated herein by reference. |

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| (7) | Filed as an exhibit to the Company’s Proxy Statement on Schedule 14A, filed on March 29, 2004, and incorporated herein by reference. |

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| (8) | Filed as an exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2004, filed on March 31, 2005, and incorporated herein by reference. |

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| (9) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on October 19, 2005, and incorporated herein by reference. |

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| (11) | Filed as an exhibit to the Company's Quarterly Report on Form 10-Q, filed on July 29, 2011, and incorporated herein by reference. |

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| (12) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on May 24, 2006, and incorporated herein by reference. |

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| (13) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on February 15, 2007, and incorporated herein by reference. |

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| (14) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on July 3, 2007, and incorporated herein by reference. |

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| (15) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on July 20, 2007, and incorporated herein by reference. |

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| (16) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on January 4, 2008, and incorporated herein by reference. |

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| (17) | Filed as an exhibit to the Company's Quarterly Report on Form 10-Q, filed on July 29, 2011, and incorporated herein by reference. |

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| (18) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on August 19, 2008, and incorporated herein by reference. |

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| (19) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on September 9, 2008, and incorporated herein by reference. |

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| (20) | Filed as an exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2008, filed on March 16, 2009, and incorporated herein by reference. |

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| (21) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on October 23, 2009, and incorporated herein by reference. |

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| (22) | Filed as an exhibit to the Company’s Annual Report on Form 10-K for the year ended December 31, 2009, filed on March 16, 2010, and incorporated herein by reference. |

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| (23) | Filed as an exhibit to the Company’s Current Report on Form 8-K, filed on January 10, 2011, and incorporated herein by reference. |

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| (24) | Filed as an exhibit to the Company's Quarterly Report on Form 10-Q, filed on November 2, 2010, and incorporated herein by reference. |

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| (25) | Certain schedules and exhibits referenced in this exhibit have been omitted in accordance with Item 601(b)(2) of Regulation S-K. A copy of any omitted schedule and/or exhibit will be furnished to the SEC upon request. |

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| (26) | Filed as an exhibit to the Company's Annual Report of Form 10-K, filed on February 27, 2013, and incorporated herein by reference. |

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| † | The Company has requested confidential treatment with respect to portions of this exhibit. |