Document:

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                                                                   EXHIBIT 4.4.3

                          REGISTRATION RIGHTS AGREEMENT

          This Registration Rights Agreement (this "Agreement") is made and
                                                    ---------
entered into as of March 15, 2002, by and between Questcor Pharmaceuticals, Inc.
a California corporation (the "Company"), and Defiante Farmaceutica Unipessoal
                               -------
L.D.A., a Portuguese company (the "Purchaser").
                                   ---------

          This Agreement is made pursuant to the Securities Purchase Agreement,
dated as of the date hereof among the Company and the Purchaser (the "Purchase
                                                                      --------
Agreement").
---------

          The Company and the Purchaser hereby agree as follows:

          1. Definitions. Capitalized terms used and not otherwise defined
             -----------
herein that are defined in the Purchase Agreement shall have the meanings given
such terms in the Purchase Agreement. As used in this Agreement, the following
terms shall have the following meanings:

          "Debentures" means the 8% Convertible Debentures issued to the
           ----------
Purchaser in accordance with the Purchase Agreement.

          "Effectiveness Date" means the earlier of (a) the 90th day following
           ------------------
the Closing Date (or the 120th day if the Commission notifies the Company that
it will be subject to a second comment letter) and (b) the fifth Trading Day
following the date on which the Company is notified by the Commission that such
Registration Statement will not be reviewed or is no longer subject to further
review and comments.

          "Effectiveness Period" shall have the meaning set forth in Section
           --------------------
2(a).

          "Filing Date" means, with respect to the initial Registration
           -----------
Statement required to be filed hereunder, the 30th day following the Closing
Date.

          "Holder" or "Holders" means the holder or holders, as the case may be,
           ------      -------
from time to time of Registrable Securities.

          "Indemnified Party" shall have the meaning set forth in Section 5(c).
           -----------------

          "Indemnifying Party" shall have the meaning set forth in Section 5(c).
           ------------------

          "Losses" shall have the meaning set forth in Section 5(a).
           ------

          "Proceeding" means an action, claim, suit, investigation or proceeding
           ----------
(including, without limitation, an investigation or partial proceeding, such as
a deposition), whether commenced or threatened.

          "Prospectus" means the prospectus included in a Registration Statement
           ----------
(including, without limitation, a prospectus that includes any information
previously omitted from a prospectus filed as part of an effective registration
statement in reliance upon Rule 430A promulgated under the Securities Act), as
amended or supplemented by any prospectus

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supplement, with respect to the terms of the offering of any portion of the
Registrable Securities covered by the Registration Statement, and all other
amendments and supplements to the Prospectus, including post-effective
amendments, and all material incorporated by reference or deemed to be
incorporated by reference in such Prospectus.

          "Registrable Securities" means the shares of Common Stock issuable
           ----------------------
upon: (i) conversion of the Debentures and (ii) exercise of the Warrants.

          "Registration Statement" means the initial registration statement
           ----------------------
required to be filed hereunder and any additional registration statements
contemplated by Section 2(d), including (in each case) the Prospectus,
                ------------
amendments and supplements to such registration statement or Prospectus,
including pre- and post-effective amendments, all exhibits thereto, and all
material incorporated by reference or deemed to be incorporated by reference in
such registration statement.

          "Rule 144" means Rule 144 promulgated by the Commission pursuant to
           --------
the Securities Act, as such Rule may be amended from time to time, or any
similar rule or regulation hereafter adopted by the Commission having
substantially the same effect as such Rule.

          "Rule 415" means Rule 415 promulgated by the Commission pursuant to
           --------
the Securities Act, as such Rule may be amended from time to time, or any
similar rule or regulation hereafter adopted by the Commission having
substantially the same effect as such Rule.

          "Rule 424" means Rule 424 promulgated by the Commission pursuant to
           --------
the Securities Act, as such Rule may be amended from time to time, or any
similar rule or regulation hereafter adopted by the Commission having
substantially the same effect as such Rule.

          "Warrants" means the Common Stock purchase warrants issued under the
           --------
Purchase Agreement.

          2. Registration.
             ------------

               (a) On or prior to the Filing Date, the Company shall prepare and
file with the Commission a Registration Statement covering the resale of not
less than 2,025,316 Registrable Securities for an offering to be made on a
continuous basis pursuant to Rule 415. The Registration Statement shall be on
Form S-3 (except if the Company is not then eligible to register for resale the
Registrable Securities on Form S-3, in which case such registration shall be on
another appropriate form in accordance herewith) and shall contain (except if
otherwise required by the Commission) the "Plan of Distribution" attached hereto
                                           --------------------
as Annex A. The Company shall use commercially reasonable efforts to cause the
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Registration Statement to become effective and remain effective as provided
herein. The Company shall use commercially reasonable efforts to cause the
Registration Statement to be declared effective under the Securities Act as
promptly as possible after the filing thereof, but in any event prior to its
Effectiveness Date, and shall use commercially reasonable efforts to keep the
Registration Statement continuously effective under the Securities Act until the
date which is the earlier date when all Registrable Securities covered by such
Registration Statement have been sold or may be sold without volume restrictions
pursuant to Rule 144(k) as determined by the counsel to the

                                      -2-

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Company pursuant to a written opinion letter to such effect, addressed and
acceptable to the Company's transfer agent and the affected Holders (the
"Effectiveness Period").
---------------------

               (b) The Company shall give written notice to the Holders of the
Registrable Securities (which notice pursuant to clauses (ii)-(v) hereof shall
be accompanied by an instruction to suspend the use of the Prospectus pursuant
to the terms of Section 2(b)(v) and is referred to herein as a "Deferral
Notice"):

                    (i) when the Registration Statement or any amendment thereto
has been filed with the Commission and when the Registration Statement or any
post-effective amendment thereto has become effective;

                    (ii) of any request by the Commission for amendments or
supplements to the Registration Statement or the prospectus included therein or
for additional information;

                    (iii) of the issuance by the Commission of any stop order
suspending the effectiveness of the Registration Statement or the initiation of
any proceedings for that purpose;

                    (iv) of the receipt by the Company or its legal counsel of
any notification with respect to the suspension of the qualification of the
Registrable Securities for sale in any jurisdiction; and

                    (v) of (A) the happening of any event that requires the
Company to make changes in the Registration Statement or the Prospectus in order
that the Registration Statement or the Prospectus does not contain an untrue
statement of a material fact nor omit to state a material fact required to be
stated therein or necessary to make the statements therein (in the case of the
Prospectus, in light of the circumstances under which they were made) not
misleading, or (B) the occurrence or existence of any pending corporate
development, public filing with the Commission or other similar event with
respect to the Company that, in the reasonable discretion of the Company, makes
it necessary to suspend the availability of a Registration Statement and the
related Prospectus.

                    The Company shall be entitled to exercise its right to
deliver a Deferral Notice under this Section 2(b) to suspend the availability of
the Registration Statement or any prospectus, without incurring or accruing any
obligation to pay liquidated damages pursuant to Section 2(c) (except for a
Deferral Notice pursuant to Section 2(b)(v)(B) for which the Company shall
remain obligated to pay liquidated damages), for one or more periods not to
exceed ten (10) consecutive days in any 120-day period, and not to exceed, in
the aggregate, thirty (30) days in any 365-day period (such period during which
the availability of the Registration Statement and any prospectus is suspended
being a "Deferral Period").

               (c) If: (a) any Registration Statement is not filed on or prior
to the Filing Date or (b) a Registration Statement filed hereunder is not
declared effective by the Commission by the Effectiveness Date, or (c) after a
Registration Statement is filed with and

                                      -3-

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declared effective by the Commission, such Registration Statement ceases to be
effective as to all Registrable Securities to which it is required to relate at
any time prior to the expiration of the Effectiveness Period without being
succeeded within fifteen Trading Days by an amendment to such Registration
Statement or by a subsequent Registration Statement filed with and declared
effective by the Commission or (d) the Common Stock is not listed or quoted, or
is suspended from trading on the American Stock Exchange for a period of two
consecutive Trading Days (any such failure or breach being referred to as an
"Event," and for purposes of clause (a) or (b) the date on which such Event
 -----
occurs, or for purposes of clause (c) the date which such fifteen Trading
Day-period is exceeded, being referred to as "Event Date"), then beginning on
                                              ----------
each such Event Date the Company shall pay to each Holder an amount in cash, as
liquidated damages and not as a penalty, equal to 1.00% per 30 day period of the
aggregate principal amount of the Debenture held by such Holder pursuant to the
Purchase Agreement, which shall accrue on a daily basis until the applicable
Event shall have been cured, during the first 90 day period, and increasing to
2.00% per 30 day period thereafter, of the aggregate principal amount of the
Debenture held by such Holder pursuant to the Purchase Agreement, which shall
accrue on a daily basis until the applicable Event shall have been cured.
Notwithstanding the foregoing, an Event Date shall be deemed not to have
occurred and be continuing in relation to the Registration Statement or the
related Prospectus if the Company has delivered a Deferral Notice pursuant to
Section 2(b) of this Agreement and the Deferral Period shall not have extended
past the periods permitted by Section 2(b)(v). If the Company fails to pay any
liquidated damages pursuant to this Section in full within seven days after the
date payable, the Company will pay interest thereon at a rate of 18% per annum
(or such lesser maximum amount that is permitted to be paid by applicable law)
to the Holder, accruing daily from the date such liquidated damages are due
until such amounts, plus all such interest thereon, are paid in full.

          3. Registration Procedures
             -----------------------

          In connection with the Company's registration obligations hereunder,
the Company shall:

               (a) Not less than two Trading Days prior to the filing of the
Registration Statement or any related Prospectus or any amendment or supplement
thereto, the Company shall, (i) furnish to the Holders copies of all such
documents proposed to be filed (including documents incorporated or deemed
incorporated by reference) which documents will be subject to the review of such
Holders, and (ii) cause its officers and directors, counsel and independent
certified public accountants to respond to such inquiries from Holders as shall
be necessary, in the reasonable opinion of respective counsel to enable the
Holder to conduct a reasonable investigation within the meaning of the
Securities Act.

               (b) (i) Prepare and file with the Commission such amendments,
including post-effective amendments, to the Registration Statement and the
Prospectus used in connection therewith as may be necessary to keep the
Registration Statement continuously effective as to the applicable Registrable
Securities for the Effectiveness Period and prepare and file with the Commission
such additional Registration Statements in order to register for resale under
the Securities Act all of the Registrable Securities; (ii) cause the related
Prospectus to be amended or supplemented by any required Prospectus supplement,
and as so supplemented or amended to be filed pursuant to Rule 424; (iii)
respond as promptly as reasonably possible, and

                                      -4-

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in any event within twenty days, to any comments received from the Commission
with respect to the Registration Statement or any amendment thereto and, as
promptly as reasonably possible provide the Holders true and complete copies of
all correspondence from and to the Commission relating to the Registration
Statement; and (iv) comply in all material respects with the provisions of the
Securities Act and the Exchange Act with respect to the disposition of all
Registrable Securities covered by the Registration Statement during the
applicable period in accordance with the intended methods of disposition by the
Holders thereof set forth in the Registration Statement as so amended or in such
Prospectus as so supplemented.

               (c) Notify the Holders of Registrable Securities to be sold as
promptly as reasonably possible (and, in the case of (i)(A) below, not less than
three Trading Days prior to such filing) and (if requested by any such Person)
confirm such notice in writing no later than one Trading Day following the day
(i)(A) when a Prospectus or any Prospectus supplement or post-effective
amendment to the Registration Statement is proposed to be filed; (B) when the
Commission notifies the Company whether there will be a "review" of such
Registration Statement and whenever the Commission comments in writing on such
Registration Statement (the Company shall provide true and complete copies
thereof and all written responses thereto to each of the Holders); and (C) with
respect to the Registration Statement or any post-effective amendment, when the
same has become effective; (ii) of any request by the Commission or any other
Federal or state governmental authority for amendments or supplements to the
Registration Statement or Prospectus or for additional information; (iii) of the
issuance by the Commission of any stop order suspending the effectiveness of the
Registration Statement covering any or all of the Registrable Securities or the
initiation of any Proceedings for that purpose; (iv) of the receipt by the
Company of any notification with respect to the suspension of the qualification
or exemption from qualification of any of the Registrable Securities for sale in
any jurisdiction, or the initiation or threatening of any Proceeding for such
purpose; and (v) of the occurrence of any event or passage of time that makes
the financial statements included in the Registration Statement ineligible for
inclusion therein or any statement made in the Registration Statement or
Prospectus or any document incorporated or deemed to be incorporated therein by
reference untrue in any material respect or that requires any revisions to the
Registration Statement, Prospectus or other documents so that, in the case of
the Registration Statement or the Prospectus, as the case may be, it will not
contain any untrue statement of a material fact or omit to state any material
fact required to be stated therein or necessary to make the statements therein,
in light of the circumstances under which they were made, not misleading;
provided that if the Company notifies the Holders in accordance with paragraphs
(ii) through (v) of Section 2(b) above to suspend the use of the Prospectus
until the end of the Deferral Period, then the Initial Purchasers and the
Holders shall suspend use of such prospectus until the Company has notified the
Holders in accordance with Section 6(d).

               (d) Use best efforts to avoid the issuance of, or, if issued,
obtain the withdrawal of (i) any order suspending the effectiveness of the
Registration Statement, or (ii) any suspension of the qualification (or
exemption from qualification) of any of the Registrable Securities for sale in
any jurisdiction, at the earliest practicable moment.

               (e) Furnish to each Holder, without charge, at least one
conformed copy of the Registration Statement and each amendment thereto,
including financial statements and schedules, all documents incorporated or
deemed to be incorporated therein by reference,

                                      -5-

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and all exhibits to the extent requested by such Person (including those
previously furnished or incorporated by reference) promptly after the filing of
such documents with the Commission.

               (f) Promptly deliver to each Holder, without charge, as many
copies of the Prospectus or Prospectuses (including each form of prospectus) and
each amendment or supplement thereto as such Persons may reasonably request. The
Company hereby consents to the use of such Prospectus and each amendment or
supplement thereto by each of the selling Holders in connection with the
offering and sale of the Registrable Securities covered by such Prospectus and
any amendment or supplement thereto.

               (g) Prior to any public offering of Registrable Securities, use
commercially reasonable efforts to register or qualify or cooperate with the
selling Holders in connection with the registration or qualification (or
exemption from such registration or qualification) of such Registrable
Securities for offer and sale under the securities or Blue Sky laws of such
jurisdictions within the United States as any Holder requests in writing, to
keep each such registration or qualification (or exemption therefrom) effective
during the Effectiveness Period and to do any and all other acts or things
necessary or advisable to enable the disposition in such jurisdictions of the
Registrable Securities covered by a Registration Statement; provided, that the
                                                            --------
Company shall not be required to qualify generally to do business in any
jurisdiction where it is not then so qualified or subject the Company to any tax
in any such jurisdiction where it is not then so subject.

               (h) Cooperate with the Holders to facilitate the timely
preparation and delivery of certificates representing Registrable Securities to
be delivered to a transferee pursuant to a Registration Statement, which
certificates shall be free, to the extent permitted by the Purchase Agreement,
of all restrictive legends, and to enable such Registrable Securities to be in
such denominations and registered in such names as any such Holders may request.

               (i) Upon the occurrence of any event contemplated by Section
3(c)(v), as promptly as reasonably possible, prepare a supplement or amendment,
including a post-effective amendment, to the Registration Statement or a
supplement to the related Prospectus or any document incorporated or deemed to
be incorporated therein by reference, and file any other required document so
that, as thereafter delivered, neither the Registration Statement nor such
Prospectus will contain an untrue statement of a material fact or omit to state
a material fact required to be stated therein or necessary to make the
statements therein, in light of the circumstances under which they were made,
not misleading.

               (j) Comply with all applicable rules and regulations of the
Commission.

               (k) The Company may require each Holder of Registrable Securities
to be sold pursuant to the Registration Statement to furnish to the Company such
information regarding the Holder and the distribution of the Registrable
Securities as the Company may from time to time be reasonably required to
include in the Registration Statement, and the Company may exclude from such
registration the Registrable Securities of any Holder that unreasonably fails to
furnish such information within a reasonable time after receiving such request.

                                      -6-

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          4. Registration Expenses. All fees and expenses incident to the
             ---------------------
performance of or compliance with this Agreement by the Company shall be borne
by the Company whether or not any Registrable Securities are sold pursuant to
the Registration Statement. The fees and expenses referred to in the foregoing
sentence shall include, without limitation, (i) all registration and filing fees
(including, without limitation, fees and expenses (A) with respect to filings
required to be made with the Trading Market on which the Common Stock is then
listed for trading, and (B) in compliance with applicable state securities or
Blue Sky laws), (ii) expenses of printing certificates for Registrable
Securities (iii) messenger, telephone and delivery expenses, (iv) Securities Act
liability insurance, if the Company so desires such insurance, and (v) fees and
expenses of all other Persons retained by the Company in connection with the
consummation of the transactions contemplated by this Agreement. In addition,
the Company shall be responsible for all of its internal expenses incurred in
connection with the consummation of the transactions contemplated by this
Agreement (including, without limitation, all salaries and expenses of its
officers and employees performing legal or accounting duties), the expense of
any annual audit and the fees and expenses incurred in connection with the
listing of the Registrable Securities on any securities exchange as required
hereunder.

          5. Indemnification
             ---------------

               (a) Indemnification by the Company. The Company shall,
                   ------------------------------
notwithstanding any termination of this Agreement, indemnify and hold harmless
each Holder, the officers, directors, agents, brokers, investment advisors and
employees of each of them, each Person who controls any such Holder (within the
meaning of Section 15 of the Securities Act or Section 20 of the Exchange Act)
and the officers, directors, agents and employees of each such controlling
Person, to the fullest extent permitted by applicable law, from and against any
and all losses, claims, damages, liabilities, costs (including, without
limitation, reasonable costs of preparation and reasonable attorneys' fees) and
expenses (collectively, "Losses"), as incurred, arising out of or relating to
                         ------
any untrue or alleged untrue statement of a material fact contained in the
Registration Statement, any Prospectus or any form of prospectus or in any
amendment or supplement thereto or in any preliminary prospectus, or arising out
of or relating to any omission or alleged omission of a material fact required
to be stated therein or necessary to make the statements therein (in the case of
any Prospectus or form of prospectus or supplement thereto, in light of the
circumstances under which they were made) not misleading, except to the extent,
but only to the extent, that (1) such untrue statements or omissions are based
solely upon information regarding such Holder furnished in writing to the
Company by such Holder expressly for use therein, or to the extent that such
information relates to such Holder or such Holder's proposed method of
distribution of Registrable Securities and was reviewed and expressly approved
in writing by such Holder expressly for use in the Registration Statement, such
Prospectus or such form of Prospectus or in any amendment or supplement thereto
(it being understood that the Holder has approved Annex A hereto for this
purpose) or (2) in the case of an occurrence of an event of the type specified
in Section 3(c)(ii)-(v), the use by such Holder of an outdated or defective
Prospectus after the Company has notified such Holder in writing that the
Prospectus is outdated or defective and prior to the receipt by such Holder of
the Advice contemplated in Section 6(d). The Company shall notify the Holders
promptly of the institution, threat or assertion of any Proceeding of which the
Company is aware in connection with the transactions contemplated by this
Agreement.

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               (b) Indemnification by Holders. Each Holder shall, severally and
                   --------------------------
not jointly, indemnify and hold harmless the Company, its directors, officers,
agents and employees, each Person who controls the Company (within the meaning
of Section 15 of the Securities Act and Section 20 of the Exchange Act), and the
directors, officers, agents or employees of such controlling Persons, to the
fullest extent permitted by applicable law, from and against all Losses, as
incurred, arising solely out of or based solely upon: (x) such Holder's failure
to comply with the prospectus delivery requirements of the Securities Act or (y)
any untrue statement of a material fact contained in any Registration Statement,
any Prospectus, or any form of prospectus, or in any amendment or supplement
thereto, or arising solely out of or based solely upon any omission of a
material fact required to be stated therein or necessary to make the statements
therein not misleading to the extent, but only to the extent, that such untrue
statement or omission is contained in any information so furnished in writing by
such Holder to the Company specifically for inclusion in such Registration
Statement or such Prospectus or to the extent that (1) such untrue statements or
omissions are based solely upon information regarding such Holder furnished in
writing to the Company by such Holder expressly for use therein, or to the
extent that such information relates to such Holder or such Holder's proposed
method of distribution of Registrable Securities and was reviewed and expressly
approved in writing by such Holder expressly for use in the Registration
Statement (it being understood that the Holder has approved Annex A hereto for
this purpose), such Prospectus or such form of Prospectus or in any amendment or
supplement thereto or (2) in the case of an occurrence of an event of the type
specified in Section 3(c)(ii)-(v), the use by such Holder of an outdated or
defective Prospectus after the Company has notified such Holder in writing that
the Prospectus is outdated or defective and prior to the receipt by such Holder
of the Advice contemplated in Section 6(d). In no event shall the liability of
any selling Holder hereunder be greater in amount than the dollar amount of the
net proceeds received by such Holder upon the sale of the Registrable Securities
giving rise to such indemnification obligation.

               (c) Conduct of Indemnification Proceedings. If any Proceeding
                   --------------------------------------
shall be brought or asserted against any Person entitled to indemnity hereunder
(an "Indemnified Party"), such Indemnified Party shall promptly notify the
     -----------------
Person from whom indemnity is sought (the "Indemnifying Party") in writing, and
                                           ------------------
the Indemnifying Party shall assume the defense thereof, including the
employment of counsel reasonably satisfactory to the Indemnified Party and the
payment of all fees and expenses incurred in connection with defense thereof;
provided, that the failure of any Indemnified Party to give such notice shall
not relieve the Indemnifying Party of its obligations or liabilities pursuant to
this Agreement, except (and only) to the extent that it shall be finally
determined by a court of competent jurisdiction (which determination is not
subject to appeal or further review) that such failure shall have proximately
and materially adversely prejudiced the Indemnifying Party.

          An Indemnified Party shall have the right to employ separate counsel
in any such Proceeding and to participate in the defense thereof, but the fees
and expenses of such counsel shall be at the expense of such Indemnified Party
or Parties unless: (1) the Indemnifying Party has agreed in writing to pay such
fees and expenses; (2) the Indemnifying Party shall have failed promptly to
assume the defense of such Proceeding and to employ counsel reasonably
satisfactory to such Indemnified Party in any such Proceeding; or (3) the named
parties to any such Proceeding (including any impleaded parties) include both
such Indemnified Party and the Indemnifying Party, and such Indemnified Party
shall have been advised by counsel that a

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conflict of interest is likely to exist if the same counsel were to represent
such Indemnified Party and the Indemnifying Party (in which case, if such
Indemnified Party notifies the Indemnifying Party in writing that it elects to
employ separate counsel at the expense of the Indemnifying Party, the
Indemnifying Party shall not have the right to assume the defense thereof and
such counsel shall be at the expense of the Indemnifying Party). The
Indemnifying Party shall not be liable for any settlement of any such Proceeding
effected without its written consent, which consent shall not be unreasonably
withheld. No Indemnifying Party shall, without the prior written consent of the
Indemnified Party, effect any settlement of any pending Proceeding in respect of
which any Indemnified Party is a party, unless such settlement includes an
unconditional release of such Indemnified Party from all liability on claims
that are the subject matter of such Proceeding.

          All fees and expenses of the Indemnified Party (including reasonable
fees and expenses to the extent incurred in connection with investigating or
preparing to defend such Proceeding in a manner not inconsistent with this
Section) shall be paid to the Indemnified Party, as incurred, within ten Trading
Days of written notice thereof to the Indemnifying Party (regardless of whether
it is ultimately determined that an Indemnified Party is not entitled to
indemnification hereunder; provided, that the Indemnifying Party may require
                           --------
such Indemnified Party to undertake to reimburse all such fees and expenses to
the extent it is finally judicially determined that such Indemnified Party is
not entitled to indemnification hereunder).

               (d) Contribution. If a claim for indemnification under Section
                   ------------
5(a) or 5(b) is unavailable to an Indemnified Party (by reason of public policy
or otherwise), then each Indemnifying Party, in lieu of indemnifying such
Indemnified Party, shall contribute to the amount paid or payable by such
Indemnified Party as a result of such Losses, in such proportion as is
appropriate to reflect the relative fault of the Indemnifying Party and
Indemnified Party in connection with the actions, statements or omissions that
resulted in such Losses as well as any other relevant equitable considerations.
The relative fault of such Indemnifying Party and Indemnified Party shall be
determined by reference to, among other things, whether any action in question,
including any untrue or alleged untrue statement of a material fact or omission
or alleged omission of a material fact, has been taken or made by, or relates to
information supplied by, such Indemnifying Party or Indemnified Party, and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such action, statement or omission. The amount paid or
payable by a party as a result of any Losses shall be deemed to include, subject
to the limitations set forth in Section 5(c), any reasonable attorneys' or other
reasonable fees or expenses incurred by such party in connection with any
Proceeding to the extent such party would have been indemnified for such fees or
expenses if the indemnification provided for in this Section was available to
such party in accordance with its terms.

          The parties hereto agree that it would not be just and equitable if
contribution pursuant to this Section 5(d) were determined by pro rata
                                                              --- ----
allocation or by any other method of allocation that does not take into account
the equitable considerations referred to in the immediately preceding paragraph.
Notwithstanding the provisions of this Section 5(d), no Holder shall be required
to contribute, in the aggregate, any amount in excess of the amount by which the
proceeds actually received by such Holder from the sale of the Registrable
Securities subject to the Proceeding exceeds the amount of any damages that such
Holder has otherwise

                                      -9-

<PAGE>

been required to pay by reason of such untrue or alleged untrue statement or
omission or alleged omission.

          The indemnity and contribution agreements contained in this Section
are in addition to any liability that the Indemnifying Parties may have to the
Indemnified Parties.

          6. Miscellaneous
             -------------

               (a) Remedies. In the event of a breach by the Company or by a
                   --------
Holder, of any of their obligations under this Agreement, each Holder or the
Company, as the case may be, in addition to being entitled to exercise all
rights granted by law and under this Agreement, including recovery of damages,
will be entitled to specific performance of its rights under this Agreement. The
Company and each Holder agree that monetary damages would not provide adequate
compensation for any losses incurred by reason of a breach by it of any of the
provisions of this Agreement and hereby further agrees that, in the event of any
action for specific performance in respect of such breach, it shall waive the
defense that a remedy at law would be adequate.

               (b) No Piggyback on Registrations. Except as and to the extent
                   -----------------------------
specified in Schedule 6(b) hereto, neither the Company nor any of its security
             -------------
holders (other than the Holders in such capacity pursuant hereto) may include
securities of the Company in the Registration Statement other than the
Registrable Securities, and the Company shall not after the date hereof enter
into any agreement providing any such right to any of its security holders.
Except as and to the extent specified in Schedule 6(b) hereto, the Company has
                                         -------------
not previously entered into any agreement granting any registration rights with
respect to any of its securities to any Person which have not been fully
satisfied.

               (c) Compliance. Each Holder covenants and agrees that it will
                   ----------
comply with the prospectus delivery requirements of the Securities Act as
applicable to it in connection with sales of Registrable Securities pursuant to
the Registration Statement.

               (d) Discontinued Disposition. Each Holder agrees by its
                   ------------------------
acquisition of such Registrable Securities that, upon receipt of a notice from
the Company of the occurrence of any event of the kind described in Section
3(c), such Holder will forthwith discontinue disposition of such Registrable
Securities under the Registration Statement until such Holder's receipt of the
copies of the supplemented Prospectus and/or amended Registration Statement or
until it is advised in writing (the "Advice") by the Company that the use of the
                                     ------
applicable Prospectus may be resumed, and, in either case, has received copies
of any additional or supplemental filings that are incorporated or deemed to be
incorporated by reference in such Prospectus or Registration Statement. The
Company may provide appropriate stop orders to enforce the provisions of this
paragraph.

               (e) Piggy-Back Registrations. If at any time during the
                   ------------------------
Effectiveness Period there is not an effective Registration Statement covering
all of the Registrable Securities and the Company shall determine to prepare and
file with the Commission a registration statement relating to an offering for
its own account or the account of others under the Securities Act of any of its
equity securities, other than on Form S-4 or Form S-8 (each as promulgated

                                      -10-

<PAGE>

under the Securities Act) or their then equivalents relating to equity
securities to be issued solely in connection with any acquisition of any entity
or business or equity securities issuable in connection with stock option or
other employee benefit plans, then the Company shall send to each Holder written
notice of such determination and, if within fifteen days after receipt of such
notice, any such Holder shall so request in writing, the Company shall include
in such registration statement all or any part of such Registrable Securities
such holder requests to be registered, subject to customary underwriter cutbacks
applicable to all holders of registration rights.

               (f) Amendments and Waivers. The provisions of this Agreement,
                   ----------------------
including the provisions of this sentence, may not be amended, modified or
supplemented, and waivers or consents to departures from the provisions hereof
may not be given, unless the same shall be in writing and signed by the Company
and a majority of the Holders of the then outstanding Registrable Securities.
Notwithstanding the foregoing, a waiver or consent to depart from the provisions
hereof with respect to a matter that relates exclusively to the rights of
certain Holders and that does not directly or indirectly affect the rights of
other Holders may be given by Holders of at least a majority of the Registrable
Securities to which such waiver or consent relates; provided, however, that the
                                                    --------  -------
provisions of this sentence may not be amended, modified, or supplemented except
in accordance with the provisions of the immediately preceding sentence.

               (g) Notices. Any and all notices or other communications or
                   -------
deliveries required or permitted to be provided hereunder shall be in writing
and shall be deemed given and effective on the earliest of (i) the date of
transmission, if such notice or communication is delivered via facsimile at the
facsimile telephone number specified in this Section prior to 6:30 p.m. (New
York City time) on a Trading Day, (ii) the Trading Day after the date of
transmission, if such notice or communication is delivered via facsimile at the
facsimile telephone number specified in this Agreement later than 6:30 p.m. (New
York City time) on any date and earlier than 11:59 p.m. (New York City time) on
such date, (iii) the Trading Day following the date of mailing, if sent by
nationally recognized overnight courier service, or (iv) upon actual receipt by
the party to whom such notice is required to be given. The address for such
notices and communications shall be as follows:

     If to the Company:    Questcor Pharmaceuticals, Inc.
                           Attention: President
                           3620 Whipple Road
                           Union City, California  94587
                           Fax: 510-400-0799

     If to the Purchaser:  Defiante Farmaceutica Unipessoal L.D.A.
                           Rua dos Ferreiros, 260 Funchal- Madeira
                            (Portogallo) 9000-082
                           Attn: Mr. Pedro Quintas

                           With copy to:

                                      -11-

<PAGE>

                           Attn: Mr. Antonio Nicolai
                           c/o Via Sudafrica, 20
                           00144 - Rome (Italy)
                           Fax: 0039.06.54229457

     If to any other Person who is then the registered Holder:

                    To the address of such Holder as it appears in the stock
                    transfer books of the Company

or such other address as may be designated in writing hereafter, in the same
manner, by such Person.

               (h) Successors and Assigns. This Agreement shall inure to the
                   ----------------------
benefit of and be binding upon the successors and permitted assigns of each of
the parties and shall inure to the benefit of each Holder. The Company may not
assign its rights or obligations hereunder without the prior written consent of
each Holder. Each Holder may assign their respective rights hereunder in the
manner and to the Persons as permitted under the Purchase Agreement.

               (i) Execution and Counterparts. This Agreement may be executed in
                   --------------------------
any number of counterparts, each of which when so executed shall be deemed to be
an original and, all of which taken together shall constitute one and the same
Agreement. In the event that any signature is delivered by facsimile
transmission, such signature shall create a valid binding obligation of the
party executing (or on whose behalf such signature is executed) the same with
the same force and effect as if such facsimile signature were the original
thereof.

               (j) Governing Law. All questions concerning the construction,
                   -------------
validity, enforcement and interpretation of this Agreement shall be governed by
and construed and enforced in accordance with the internal laws of the State of
New York, without regard to the principles of conflicts of law thereof. Each
party hereto hereby irrevocably waives personal service of process and consents
to process being served in any such Proceeding by mailing a copy thereof via
registered or certified mail or overnight delivery (with evidence of delivery)
to such party at the address in effect for notices to it under this Agreement
and agrees that such service shall constitute good and sufficient service of
process and notice thereof. Nothing contained herein shall be deemed to limit in
any way any right to serve process in any manner permitted by law. Each party
hereto hereby irrevocably waives, to the fullest extent permitted by applicable
law, any and all right to trial by jury in any legal proceeding arising out of
or relating to this Agreement or the transactions contemplated hereby. If either
party shall commence a Proceeding to enforce any provisions of a Transaction
Document, then the prevailing party in such Proceeding shall be reimbursed by
the other party for its reasonable attorneys fees and other costs and expenses
incurred with the investigation, preparation and prosecution of such Proceeding.

               (k) Cumulative Remedies. The remedies provided herein are
                   -------------------
cumulative and not exclusive of any remedies provided by law.

                                      -12-

<PAGE>

               (l) Severability. If any term, provision, covenant or restriction
                   ------------
of this Agreement is held by a court of competent jurisdiction to be invalid,
illegal, void or unenforceable, the remainder of the terms, provisions,
covenants and restrictions set forth herein shall remain in full force and
effect and shall in no way be affected, impaired or invalidated, and the parties
hereto shall use their reasonable efforts to find and employ an alternative
means to achieve the same or substantially the same result as that contemplated
by such term, provision, covenant or restriction. It is hereby stipulated and
declared to be the intention of the parties that they would have executed the
remaining terms, provisions, covenants and restrictions without including any of
such that may be hereafter declared invalid, illegal, void or unenforceable.

               (m) Headings. The headings in this Agreement are for convenience
                   --------
of reference only and shall not limit or otherwise affect the meaning hereof.

               (n) Independent Nature of Purchaser's Obligations and Rights.
                   --------------------------------------------------------
Nothing contained herein or in any other agreement or document delivered at any
closing, and no action taken by the Purchaser pursuant hereto or thereto, shall
be deemed to constitute the Purchasers as a partnership, an association, a joint
venture or any other kind of entity with any other party, or create a
presumption that the Purchaser is in any way acting in concert with any third
party with respect to such obligations or the transactions contemplated by this
Agreement.

                   [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK
                            SIGNATURE PAGE TO FOLLOW]

                                      -13-

<PAGE>

          IN WITNESS WHEREOF, the parties have executed this Registration Rights
Agreement as of the date first written above.

                                     QUESTCOR PHARMACEUTICALS, INC.

                                     By:      /s/ Timothy E. Morris
                                        ---------------------------------
                                     Name:        Timothy E. Morris
                                     Title:    Chief Financial Officer

                                     DEFIANTE FARMACEUTICA
                                     UNIPESSOAL L.D.A.

                                     By:      /s/ Antonio Nicolai
                                        ---------------------------------
                                     Name:    Mr. Antonio Nicolai
                                     Title:          Director

                                      -14-

<PAGE>

Annex A
-------

Plan of Distribution
--------------------

          The selling stockholders and any of their pledgees, assignees and
successors-in-interest may, from time to time, sell any or all of their shares
of common stock on any stock exchange, market or trading facility on which the
shares are traded or in private transactions. These sales may be at fixed or
negotiated prices. The selling stockholders may use any one or more of the
following methods when selling shares:

..    ordinary brokerage transactions and transactions in which the broker-dealer
     solicits purchasers;

..    block trades in which the broker-dealer will attempt to sell the shares as
     agent but may position and resell a portion of the block as principal to
     facilitate the transaction;

..    purchases by a broker-dealer as principal and resale by the broker-dealer
     for its account;

..    an exchange distribution in accordance with the rules of the applicable
     exchange;

..    privately negotiated transactions;

..    short sales

..    broker-dealers may agree with the selling stockholders to sell a specified
     number of such shares at a stipulated price per share;

..    a combination of any such methods of sale; and

..    any other method permitted pursuant to applicable law.

          The selling stockholders may also sell shares under Rule 144 under the
Securities Act, if available, rather than under this prospectus.

          Broker-dealers engaged by the selling stockholders may arrange for
other brokers-dealers to participate in sales. Broker-dealers may receive
commissions or discounts from the selling stockholders (or, if any broker-dealer
acts as agent for the purchaser of shares, from the purchaser) in amounts to be
negotiated. The selling stockholders do not expect these commissions and
discounts to exceed what is customary in the types of transactions involved.

          The selling stockholders may from time to time pledge or grant a
security interest in some or all of the shares of common stock or Warrants owned
by them and, if they default in the performance of their secured obligations,
the pledgees or secured parties may offer and sell the shares of common stock
from time to time under this prospectus, or under an amendment to this
prospectus under Rule 424(b)(3) or other applicable provision of the Securities
Act of 1933 amending the list of selling stockholders to include the pledgee,
transferee or other successors in interest as selling stockholders under this
prospectus.

<PAGE>

          The selling stockholders also may transfer the shares of common stock
in other circumstances, in which case the transferees, pledgees or other
successors in interest will be the selling beneficial owners for purposes of
this prospectus.

          The selling stockholders and any broker-dealers or agents that are
involved in selling the shares may be deemed to be "underwriters" within the
meaning of the Securities Act in connection with such sales. In such event, any
commissions received by such broker-dealers or agents and any profit on the
resale of the shares purchased by them may be deemed to be underwriting
commissions or discounts under the Securities Act. The selling stockholders have
informed the Company that they do not have any agreement or understanding,
directly or indirectly, with any person to distribute the Common Stock.

          The Company is required to pay all fees and expenses incident to the
registration of the shares. The Company has agreed to indemnify the selling
stockholders against certain losses, claims, damages and liabilities, including
liabilities under the Securities Act.

                                       -2-<PAGE>

                                                                   EXHIBIT 4.4.4

NEITHER THESE SECURITIES NOR THE SECURITIES INTO WHICH THESE SECURITIES ARE
EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR
THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM
REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES
ACT"), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN
EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR PURSUANT TO AN
AVAILABLE EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE REGISTRATION
REQUIREMENTS OF THE SECURITIES ACT AND IN ACCORDANCE WITH APPLICABLE STATE
SECURITIES LAWS AS EVIDENCED BY A LEGAL OPINION OF COUNSEL TO THE TRANSFEROR TO
SUCH EFFECT, THE SUBSTANCE OF WHICH SHALL BE REASONABLY ACCEPTABLE TO THE
COMPANY. THESE SECURITIES AND THE SECURITIES ISSUABLE UPON EXERCISE OF THESE
SECURITIES MAY BE PLEDGED IN CONNECTION WITH A BONA FIDE MARGIN ACCOUNT OR OTHER
LOAN SECURED BY SUCH SECURITIES.

                         QUESTCOR PHARMACEUTICALS, INC.

                                     WARRANT
                                     -------

Warrant No. 1                          Date of Original Issuance: March 15, 2002

          Questcor Pharmaceuticals, Inc., a California corporation (the
"Company"), hereby certifies that, for value received, Defiante Farmaceutica
Unipessoal L.D.A., or its registered assigns (the "Holder"), is entitled to
purchase from the Company up to a total of 759,493 shares of common stock, no
par value per share (the "Common Stock"), of the Company (each such share, a
"Warrant Share" and all such shares, the "Warrant Shares") at an exercise price
(as adjusted from time to time as provided in Section 9, the "Exercise Price")
per Warrant Share equal to $1.70, at any time and from time to time from and
after the date hereof and through and including March 15, 2006 (the "Expiration
Date"), and subject to the following terms and conditions:

     1. Definitions. In addition to the terms defined elsewhere in this Warrant,
        -----------
capitalized terms that are not otherwise defined herein and that are defined in
the Securities Purchase Agreement, dated as of March 15, 2002, between the
Company and the original Holder (the "Purchase Agreement"), shall have the
meanings given to such terms in the Purchase Agreement.

     2. Registration of Warrant. The Company shall register this Warrant, upon
        -----------------------
records to be maintained by the Company for that purpose (the "Warrant
Register"), in the name of the record Holder hereof from time to time. The
Company may deem and treat the registered Holder of this Warrant as the absolute
owner hereof for the purpose of any exercise hereof or any distribution to the
Holder, and for all other purposes, absent actual notice to the contrary.

<PAGE>

     3. Registration of Transfers. The Company shall register the transfer of
        -------------------------
any portion of this Warrant in the Warrant Register, upon surrender of this
Warrant, with the Form of Assignment attached hereto duly completed and signed,
to the Transfer Agent or to the Company at its address specified herein. Upon
any such registration or transfer, a new warrant to purchase Common Stock, in
substantially the form of this Warrant (any such new warrant, a "New Warrant"),
evidencing the portion of this Warrant so transferred shall be issued to the
transferee and a New Warrant evidencing the remaining portion of this Warrant
not so transferred, if any, shall be issued to the transferring Holder. The
acceptance of the New Warrant by the transferee thereof shall be deemed the
acceptance by such transferee of all of the rights and obligations of a holder
of a Warrant.

     4. Exercise and Duration. This Warrant shall be exercisable by the
        ---------------------
registered Holder at any time and from time to time on or after the date hereof
to and including the Expiration Date. At 6:30 p.m., New York City time on the
Expiration Date, the portion of this Warrant available for exercise and not
exercised prior thereto shall be and become void and of no value.

     5. Delivery of Warrant Shares.
        --------------------------

          (a) Upon delivery of the Form of Election to Purchase to the Company
(with the attached Warrant Shares Exercise Log) at its address for notice set
forth in Section 13 and upon payment of the Exercise Price multiplied by the
number of Warrant Shares that the Holder intends to purchase hereunder, the
Company shall promptly (but in no event later than three Trading Days after the
Date of Exercise (as defined herein)) issue and deliver to the Holder, a
certificate for the Warrant Shares issuable upon such exercise free of
restrictive legends unless otherwise required by the Purchase Agreement. The
Company shall, upon request of the Holder, if available, use its best efforts to
deliver Warrant Shares hereunder electronically through the Depository Trust
Corporation or another established clearing corporation performing similar
functions, provided, that, the Company may, but will not be required to change
its transfer agent if its current transfer agent cannot deliver Warrant Shares
electronically through the Depository Trust Corporation.

               A "Date of Exercise" means the date on which the Holder shall
have delivered to the Company (i) the Form of Election to Purchase attached
hereto (with the Warrant Exercise Log attached to it), appropriately completed
and duly signed and (ii) payment of the Exercise Price for the number of Warrant
Shares so indicated by the Holder to be purchased.

          (b) If by the fifth Trading Day after a Date of Exercise the Company
fails to deliver the required number of Warrant Shares in the manner required
pursuant to Section 5(a), then the Holder will have the right to rescind such
exercise.

          (c) If by the fifth Trading Day after a Date of Exercise the Company
fails to deliver the required number of Warrant Shares in the manner required
pursuant to Section 5(a), and if after such fifth Trading Day the Holder
purchases (in an open market transaction or otherwise) shares of Common Stock to
deliver in satisfaction of a sale by the Holder of the Warrant Shares which the
Holder anticipated receiving upon such exercise (a "Buy-In"), then the Company
shall (1) pay in cash to the Holder the amount by which (x) the Holder's total
purchase

                                       -2-

<PAGE>

price (including brokerage commissions, if any) for the shares of Common Stock
so purchased exceeds (y) the amount obtained by multiplying (A) the number of
Warrant Shares that the Company was required to deliver to the Holder in
connection with the exercise at issue by (B) the Closing Price of the Common
Stock at the time of the obligation giving rise to such purchase obligation and
(2) at the option of the Holder, either reinstate the portion of the Warrant and
equivalent number of Warrant Shares for which such exercise was not honored or
deliver to the Holder the number of shares of Common Stock that would have been
issued had the Company timely complied with its exercise and delivery
obligations hereunder. For example, if the Holder purchases Common Stock having
a total purchase price of $11,000 to cover a Buy-In with respect to an attempted
exercise of shares of Common Stock with a market price on the date of exercise
totaled $10,000, under clause (1) of the immediately preceding sentence the
Company shall be required to pay the Holder $1,000. The Holder shall provide the
Company written notice, which written notice shall include such supporting
documentation as reasonably necessary to substantiate the amounts payable,
indicating the amounts payable to the Holder in respect of the Buy-In.

          (d) The Company's obligations to issue and deliver Warrant Shares in
accordance with the terms hereof are absolute and unconditional, irrespective of
any action or inaction by the Holder to enforce the same, any waiver or consent
with respect to any provision hereof, the recovery of any judgment against any
Person or any action to enforce the same, or any setoff, counterclaim,
recoupment, limitation or termination, or any breach or alleged breach by the
Holder or any other Person of any obligation to the Company or any violation or
alleged violation of law by the Holder or any other Person, and irrespective of
any other circumstance which might otherwise limit such obligation of the
Company to the Holder in connection with the issuance of Warrant Shares. Nothing
herein shall limit a Holder's right to pursue any other remedies available to it
hereunder, at law or in equity including, without limitation, a decree of
specific performance and/or injunctive relief with respect to the Company's
failure to timely deliver certificates representing shares of Common Stock upon
exercise of the Warrant as required pursuant to the terms hereof.

     6. Charges, Taxes and Expenses. Issuance and delivery of certificates for
        ---------------------------
shares of Common Stock upon exercise of this Warrant shall be made without
charge to the Holder for any issue or transfer tax, withholding tax, transfer
agent fee or other incidental tax or expense in respect of the issuance of such
certificates, all of which taxes and expenses shall be paid by the Company;
provided, however, that the Company shall not be required to pay any tax which
may be payable in respect of any transfer involved in the registration of any
certificates for Warrant Shares or Warrants in a name other than that of the
Holder. The Holder shall be responsible for all other tax liability that may
arise as a result of holding or transferring this Warrant or receiving Warrant
Shares upon exercise hereof.

     7. Replacement of Warrant. If this Warrant is mutilated, lost, stolen or
        ----------------------
destroyed, the Company shall issue or cause to be issued in exchange and
substitution for and upon cancellation hereof, or in lieu of and substitution
for this Warrant, a New Warrant, but only upon receipt of evidence reasonably
satisfactory to the Company of such loss, theft or destruction and customary and
reasonable indemnity, if requested. Applicants for a New Warrant under such
circumstances shall also comply with such other reasonable regulations and
procedures and pay such other reasonable third-party costs as the Company may
prescribe.

                                      -3-

<PAGE>

     8. Reservation of Warrant Shares. The Company covenants that it will at all
        -----------------------------
times reserve and keep available out of the aggregate of its authorized but
unissued and otherwise unreserved Common Stock, solely for the purpose of
enabling it to issue Warrant Shares upon exercise of this Warrant as herein
provided, the number of Warrant Shares which are then issuable and deliverable
upon the exercise of this entire Warrant. The Company covenants that all Warrant
Shares so issuable and deliverable shall, upon issuance and the payment of the
applicable Exercise Price in accordance with the terms hereof, be duly and
validly authorized, issued and fully paid and nonassessable.

     9. Certain Adjustments. The Exercise Price and number of Warrant Shares
        -------------------
issuable upon exercise of this Warrant are subject to adjustment from time to
time as set forth in this Section 9.

          (a) Stock Dividends and Splits. If the Company, at any time while this
              --------------------------
Warrant is outstanding, (i) pays a stock dividend on its Common Stock or
otherwise makes a distribution on any class of capital stock that is payable in
shares of Common Stock, (ii) subdivides outstanding shares of Common Stock into
a larger number of shares, or (iii) combines outstanding shares of Common Stock
into a smaller number of shares, then in each such case the Exercise Price shall
be multiplied by a fraction of which the numerator shall be the number of shares
of Common Stock outstanding immediately before such event and of which the
denominator shall be the number of shares of Common Stock outstanding
immediately after such event.

          (b) Pro Rata Distributions. If the Company, at any time while this
              ----------------------
Warrant is outstanding, distributes to all holders of Common Stock (i) evidences
of its indebtedness, (ii) any security (other than a distribution of Common
Stock covered by the preceding paragraph), (iii) rights or warrants to subscribe
for or purchase any security, or (iv) any other asset (in each case,
"Distributed Property"), then, at the request of any Holder delivered before the
90th day after the record date fixed for determination of stockholders entitled
to receive such distribution, the Company will deliver to such Holder, within
five Trading Days after such request (or, if later, on the effective date of
such distribution), the Distributed Property that such Holder would have been
entitled to receive in respect of the Warrant Shares for which such Holder's
Warrant could have been exercised immediately prior to such record date. If such
Distributed Property is not delivered to a Holder pursuant to the preceding
sentence, then upon any exercise of the Warrant that occurs after such record
date, such Holder shall be entitled to receive, in addition to the Warrant
Shares otherwise issuable upon such conversion, the Distributed Property that
such Holder would have been entitled to receive in respect of such number of
Warrant Shares had the Holder been the record holder of such Warrant Shares
immediately prior to such record date.

          (c) Fundamental Transactions. If, at any time while this Warrant is
              ------------------------
outstanding: (i) the Company effects any merger or consolidation of the Company
with or into another Person, (ii) the Company effects any sale of all or
substantially all of its assets in one or a series of related transactions,
(iii) any tender offer or exchange offer (whether by the Company or another
Person) is completed pursuant to which holders of Common Stock are permitted to
tender or exchange their shares for other securities, cash or property, or (iv)
the Company effects any reclassification of the Common Stock or any compulsory
share exchange pursuant to which the Common Stock is effectively converted into
or exchanged for other securities, cash or

                                      -4-

<PAGE>

property (in any such case, a "Fundamental Transaction"), then the Holder shall
have the right thereafter to receive, upon exercise of this Warrant, the same
amount and kind of securities, cash or property as it would have been entitled
to receive upon the occurrence of such Fundamental Transaction if it had been,
immediately prior to such Fundamental Transaction, the holder of the number of
Warrant Shares then issuable upon exercise in full of this Warrant (the
"Alternate Consideration"). For purposes of any such exercise, the determination
of the Exercise Price shall be appropriately adjusted to apply to such Alternate
Consideration based on the amount of Alternate Consideration issuable in respect
of one share of Common Stock in such Fundamental Transaction, and the Company
shall apportion the Exercise Price among the Alternate Consideration in a
reasonable manner reflecting the relative value of any different components of
the Alternate Consideration. If holders of Common Stock are given any choice as
to the securities, cash or property to be received in a Fundamental Transaction,
then the Holder shall be given the same choice as to the Alternate Consideration
it receives upon any exercise of this Warrant following such Fundamental
Transaction. At the Holder's option and request, any successor to the Company or
surviving entity in such Fundamental Transaction shall issue to the Holder a new
warrant substantially in the form of this Warrant and consistent with the
foregoing provisions and evidencing the Holder's right to purchase the Alternate
Consideration for the aggregate Exercise Price upon exercise thereof. The terms
of any agreement pursuant to which a Fundamental Transaction is effected shall
include terms requiring any such successor or surviving entity to comply with
the provisions of this paragraph (c) and insuring that the Warrant (or any such
replacement security) will be similarly adjusted upon any subsequent transaction
analogous to a Fundamental Transaction.

          (d) Number of Warrant Shares. Simultaneously with any adjustment to
              ------------------------
the Exercise Price pursuant to paragraphs (a) or (b) of this Section, the number
of Warrant Shares that may be purchased upon exercise of this Warrant shall be
increased or decreased proportionately, so that after such adjustment the
aggregate Exercise Price payable hereunder for the adjusted number of Warrant
Shares shall be the same as the aggregate Exercise Price in effect immediately
prior to such adjustment.

          (e) Calculations. All calculations under this Section 9 shall be made
              ------------
to the nearest cent or the nearest 1/100th of a share, as applicable. The number
of shares of Common Stock outstanding at any given time shall not include shares
owned or held by or for the account of the Company, and the disposition of any
such shares shall be considered an issue or sale of Common Stock.

          (f) Notice of Adjustments. Upon the occurrence of each adjustment
              ---------------------
pursuant to this Section 9, the Company at its expense will promptly compute
such adjustment in accordance with the terms of this Warrant and prepare a
certificate setting forth such adjustment, including a statement of the adjusted
Exercise Price and adjusted number or type of Warrant Shares or other securities
issuable upon exercise of this Warrant (as applicable), describing the
transactions giving rise to such adjustments and showing in detail the facts
upon which such adjustment is based. Upon written request, the Company will
promptly deliver a copy of each such certificate to the Holder and to the
Company's Transfer Agent.

          (g) Notice of Corporate Events. If the Company (i) declares a dividend
              --------------------------
or any other distribution of cash, securities or other property in respect of
its Common Stock, including

                                      -5-

<PAGE>

without limitation any granting of rights or warrants to subscribe for or
purchase any capital stock of the Company or any Subsidiary, (ii) authorizes or
approves, enters into any agreement contemplating or solicits stockholder
approval for any Fundamental Transaction or (iii) authorizes the voluntary
dissolution, liquidation or winding up of the affairs of the Company, then the
Company shall deliver to the Holder a notice describing the material terms and
conditions of such transaction, at least twenty (20) calendar days prior to the
applicable record or effective date on which a Person would need to hold Common
Stock in order to participate in or vote with respect to such transaction, and
the Company will take all steps reasonably necessary in order to insure that the
Holder is given the practical opportunity to exercise this Warrant prior to such
time so as to participate in or vote with respect to such transaction; provided,
however, that the failure to deliver such notice or any defect therein shall not
affect the validity of the corporate action required to be described in such
notice.

     10. Payment of Exercise Price. The Holder shall pay the Exercise Price in
         -------------------------
one of the following manners:

          (a) Cash Exercise. The Holder may deliver immediately available funds;
              -------------
or

          (b) Cashless Exercise. The Holder may satisfy its obligation to pay
              -----------------
the Exercise Price through a "cashless exercise" in which event the Company
shall issue to the Holder the number of Warrant Shares determined as follows:

                    X = Y [(A-B)/A]
          where:
                    X = the number of Warrant Shares to be issued to the Holder.

                    Y = the number of Warrant Shares with
                    respect to which this Warrant is being
                    exercised.

                    A = the average of the Closing Prices for
                    the five Trading Days immediately prior to
                    (but not including) the Exercise Date.

                    B = the Exercise Price.

For purposes of Rule 144 promulgated under the Securities Act, it is intended,
understood and acknowledged that the Warrant Shares issued in a cashless
exercise transaction shall be deemed to have been acquired by the Holder, and
the holding period for the Warrant Shares shall be deemed to have commenced, on
the date this Warrant was originally issued pursuant to the Purchase Agreement.

     11. No Fractional Shares. No fractional shares of Warrant Shares will be
         --------------------
issued in connection with any exercise of this Warrant. In lieu of any
fractional shares which would, otherwise be issuable, the Company shall pay cash
equal to the product of such fraction multiplied by the Closing Price of one
Warrant Share as reported on the Eligible Market on the date of exercise.

     12. Notices. Any and all notices or other communications or deliveries
         -------
hereunder (including without limitation any Exercise Notice) shall be in writing
and shall be deemed given

                                      -6-

<PAGE>

and effective on the earliest of (i) the date of transmission, if such notice or
communication is delivered via facsimile at the facsimile number specified in
this Section prior to 6:30 p.m. (New York City time) on a Trading Day, (ii) the
next Trading Day after the date of transmission, if such notice or communication
is delivered via facsimile at the facsimile number specified in this Section on
a day that is not a Trading Day or later than 6:30 p.m. (New York City time) on
any Trading Day, (iii) the Trading Day following the date of mailing, if sent by
nationally recognized overnight courier service, or (iv) upon actual receipt by
the party to whom such notice is required to be given. The addresses for such
communications shall be: (i) if to the Company, to Questcor Pharmaceuticals,
Inc., Attention: President, 3620 Whipple Road, Union City, California 94587 or
(ii) if to the Holder, to the address or facsimile number appearing on the
Warrant Register or such other address or facsimile number as the Holder may
provide to the Company in accordance with this Section.

     13. Warrant Agent. The Company shall serve as warrant agent under this
         -------------
Warrant. Upon 30 days' notice to the Holder, the Company may appoint a new
warrant agent. Any corporation into which the Company or any new warrant agent
may be merged or any corporation resulting from any consolidation to which the
Company or any new warrant agent shall be a party or any corporation to which
the Company or any new warrant agent transfers substantially all of its
corporate trust or shareholders services business shall be a successor warrant
agent under this Warrant without any further act. Any such successor warrant
agent shall promptly cause notice of its succession as warrant agent to be
mailed (by first class mail, postage prepaid) to the Holder at the Holder's last
address as shown on the Warrant Register.

     14. Miscellaneous.
         -------------

          (a) This Warrant shall be binding on and inure to the benefit of the
parties hereto and their respective successors and assigns. Subject to the
preceding sentence, nothing in this Warrant shall be construed to give to any
Person other than the Company and the Holder any legal or equitable right,
remedy or cause of action under this Warrant. This Warrant may be amended only
in writing signed by the Company and the Holder and their successors and
assigns.

          (b) All questions concerning the construction, validity, enforcement
and interpretation of this Warrant shall be governed by and construed and
enforced in accordance with the internal laws of the State of New York, without
regard to the principles of conflicts of law thereof. Each party hereto hereby
irrevocably waives personal service of process and consents to process being
served in any such suit, action or proceeding by mailing a copy thereof via
registered or certified mail or overnight delivery (with evidence of delivery)
to such party at the address in effect for notices to it under this Warrant and
agrees that such service shall constitute good and sufficient service of process
and notice thereof. Nothing contained herein shall be deemed to limit in any way
any right to serve process in any manner permitted by law. Each party hereto
(including its affiliates, agents, officers, directors and employees) hereby
irrevocably waives, to the fullest extent permitted by applicable law, any and
all right to trial by jury in any legal proceeding arising out of or relating to
this Warrant or the transactions contemplated hereby. If either party shall
commence an action or proceeding to enforce any provisions of this Warrant, then
the prevailing party in such action or proceeding shall be

                                      -7-

<PAGE>

reimbursed by the other party for its reasonable attorneys fees and other costs
and expenses incurred with the investigation, preparation and prosecution of
such action or proceeding.

          (c) The headings herein are for convenience only, do not constitute a
part of this Warrant and shall not be deemed to limit or affect any of the
provisions hereof.

          (d) In case any one or more of the provisions of this Warrant shall be
invalid or unenforceable in any respect, the validity and enforceability of the
remaining terms and provisions of this Warrant shall not in any way be affected
or impaired thereby and the parties will attempt in good faith to agree upon a
valid and enforceable provision which shall be a commercially reasonable
substitute therefor, and upon so agreeing, shall incorporate such substitute
provision in this Warrant.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK,
                             SIGNATURE PAGE FOLLOWS]

                                      -8-

<PAGE>

          IN WITNESS WHEREOF, the Company has caused this Warrant to be duly
executed by its authorized officer as of the date first indicated above.

                                           QUESTCOR PHARMACEUTICALS,
                                           INC.

                                           By:     /s/ Timothy E. Morris
                                              ----------------------------------
                                           Name:       Timothy E. Morris
                                           Title:   Chief Financial Officer

                                      -9-

<PAGE>

                          FORM OF ELECTION TO PURCHASE

To Questcor Pharmaceuticals, Inc.:

          In accordance with Warrant No. [ ] issued to the undersigned, the
undersigned hereby elects to purchase               shares of common stock
                                      -------------
("Common Stock"), no par value per share, of Questcor Pharmaceuticals, Inc. and,
if such Holder is not utilizing the cashless exercise provisions set forth in
this Warrant, encloses herewith $         in cash, certified or official bank
                                 --------
check or checks, which sum represents the aggregate Exercise Price (as defined
in the Warrant) for the number of shares of Common Stock to which this Form of
Election to Purchase relates.

          By its delivery of this Form of Election To Purchase, the Holder
represents and warrants to the Company that in giving effect to the exercise
evidenced hereby the Holder will not beneficially own in excess of the number of
shares of Common Stock (determined in accordance with Section 13(d) of the
Securities Exchange Act of 1934) permitted to be owned under Section 11of this
Warrant to which this notice relates.

          The undersigned requests that certificates for the shares of Common
Stock issuable upon this exercise be issued in the name of

SOCIAL SECURITY OR TAX IDENTIFICATION NUMBER:
                                             ---------------------------

NAME AND ADDRESS:
                 ------------------------

                      -------------------------------

                      -------------------------------

<PAGE>

                           Warrant Shares Exercise Log
                           ---------------------------

<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------------
Date                           Number of Warrant Shares     Number of Warrant Shares    Number of Warrant Shares
                               Available to be Exercised    Exercised                   Remaining to be Exercised
-----------------------------------------------------------------------------------------------------------------
<S>                            <C>                          <C>                         <C>

-----------------------------------------------------------------------------------------------------------------
</TABLE>

<PAGE>

                               FORM OF ASSIGNMENT

           [To be completed and signed only upon transfer of Warrant]

          FOR VALUE RECEIVED, the undersigned hereby sells, assigns and
transfers unto                                  the right represented by the
               --------------------------------
within Warrant to purchase              shares of Common Stock of Questcor
                           ------------
Pharmaceuticals, Inc. to which the within Warrant relates and appoints
                 attorney to transfer said right on the books of Questcor
----------------
Pharmaceuticals, Inc. with full power of substitution in the premises.

Dated:                  ,
         ---------------  ----

                                     -------------------------------------------
                                     (Signature must conform in all respects to
                                     name of holder as specified on the face of
                                     the Warrant)

                                     -------------------------------------------
                                     Address of Transferee

                                     -------------------------------------------

                                     -------------------------------------------

In the presence of:

---------------------------------

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