Exhibit 10.5

AMENDMENT

This AMENDMENT (the “Amendment”), dated as of May 16, 2014, is made and entered
into by and between Questcor Pharmaceuticals, Inc., a California corporation
(the “Company”), and Stephen Cartt (the “Executive”).

RECITALS

WHEREAS, the Company, Mallinckrodt plc, an Irish public limited company and
Quincy Merger Sub, Inc. a Delaware corporation (the “Merger Sub”), have entered
into an Agreement and Plan of Merger (the “Merger Agreement”) pursuant to which
Merger Sub will merge with and into the Company, with the Company as the
surviving corporation of such merger (the “Merger”);

WHEREAS, the Company and the Executive are parties to (i) an Offer of Employment
letter agreement, dated March 7, 2005, as amended (the “Employment Agreement”)
and (ii) a Change in Control letter agreement, dated as of March 8, 2005, as
amended (the “CIC Agreement” and, collectively with the Employment Agreement,
the “Agreements”); and

WHEREAS, in connection with the Merger, the Company and the Executive desire to
enter into this Amendment with respect to the effect of the Merger under each
Agreement.

AMENDMENT

The parties hereto hereby amend each Agreement as follows, effective as of the
date on which the Merger Agreement is entered into (the “Effective Date”).

1.    The definition of “Good Reason” in each Agreement is hereby deleted and
replaced in its entirety with the following:

““Good Reason” shall mean the occurrence of any one or more of the following
events:

(1) Without the Executive’s written consent, assignment to the Executive of any
duties inconsistent in any material respect with the Executive’s duties or
responsibilities;

(2) Without the Executive’s written consent, a material change in the geographic
location at which the Executive must perform services to a location which is
more than 50 miles from the Executive’s principal place of business; or

(3) Without the Executive’s written consent, a material reduction in the
Executive’s base salary compensation opportunity.

Notwithstanding the foregoing, the Executive shall be considered to have a Good
Reason only if (x) the Executive provides written notice to the Company
specifying in reasonable detail the event upon which the Executive is basing
such Good Reason within ninety (90) days after the occurrence of such event, (y)
the Company fails to cure such event within thirty (30) days after its receipt
of such notice, and (z) the Executive terminates employment within sixty (60)
days after the expiration of such cure period. In addition, notwithstanding
anything to the contrary contained herein, in order to receive severance

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payments and/or benefits upon a termination of employment for Good Reason in
connection with a Change in Control, the event(s) constituting Good Reason must
occur during the period beginning sixty (60) days prior to the date of a Change
in Control and ending one (1) year after the date of such Change in Control.”

2.    To the extent applicable, each Agreement shall be deemed amended to the
extent necessary to effectuate the provisions and intent of this Amendment, and
such amendments shall be incorporated in and form a part of such agreements.

3.    In the event the Merger Agreement is terminated prior to consummation of
the Merger, this Amendment shall automatically and without further action
terminate.

4.    This Amendment shall be administered, interpreted and enforced under the
internal laws of the State of California without regard to the principles of
conflicts of laws thereof.

5.    If any provision of this Amendment is determined to be invalid or
unenforceable, it shall be adjusted rather than voided, to achieve the intent of
the parties to the extent possible, and the remainder of the Amendment shall be
enforced to the maximum extent possible.

6.    This Amendment may be executed in any number of counterparts, each of
which shall be deemed to be an original and all of which together shall
constitute one and the same instrument. The parties hereto agree to accept a
signed facsimile copy of this Amendment as a fully binding original.

(Signature page follows)

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IN WITNESS WHEREOF, this Amendment has been executed and delivered by the
parties hereto.

QUESTCOR PHARMACEUTICALS,
a California corporation

By: /s/ Don M. Bailey
Name: Don M. Bailey
Title: President and CEO

EXECUTIVE

/s/ Stephen Cartt
Stephen Cartt