Document:

<PAGE>
                                                                   EXHIBIT 10.18

                                FOURTH AMENDMENT
                                       TO
                                 ALLERGAN, INC.
                       SUPPLEMENTAL EXECUTIVE BENEFIT PLAN
                                 (RESTATED 1996)

      The ALLERGAN, INC. SUPPLEMENTAL EXECUTIVE BENEFIT PLAN (the "Plan") is
hereby amended as follows:

1.    Section 3.5 of the Plan is amended as follows:

            3.5 Claims Procedures. If a person is required by the Committee to
      submit an application for benefits under Section 3.4 or if a Participant
      or his or her beneficiary believes that he or she is being denied any
      rights or benefits under the Plan, the Participant, beneficiary, or in
      either case, his or her authorized representative (the "Claimant") shall
      follow the administrative procedures for filing a claim for benefits as
      set forth in this Section. An application for benefits or a claim for
      benefits shall be in writing and shall be reviewed by the Committee or a
      claims official designated by the Committee. The Committee or claims
      official shall review a claim for benefits in accordance with the
      procedures established by the Committee subject to the following
      administrative procedures set forth in this Section.

                  (a) The Committee shall furnish the Claimant with written or
            electronic notice of the decision rendered with respect to a claim
            for benefits within 90 days following receipt by the Committee (or
            its delegate) of the claim unless the Committee determines that
            special circumstances require an extension of time for processing
            the claim. In the event an extension is necessary, written or
            electronic notice of the extension shall be furnished to the
            Claimant prior to the expiration of the initial 90 day period. The
            notice shall indicate the special circumstances requiring an
            extension of time and the date by which a final decision is expected
            to be rendered. In no event shall the period of the extension exceed
            90 days from the end of the initial 90 day period.

                  (b) In the case of a denial of the Claimant's claim, the
            written or electronic notice of such denial shall set forth (i) the
            specific reasons for the denial, (ii) references to the Plan
            provisions upon which the denial is based, (iii) a description of
            any additional information or material necessary for perfection of
            the claim (together with an explanation why such material or
            information is necessary), (iv) an explanation of the Plan's appeals
            procedures, and (v) a statement of the Claimant's right to bring a
            civil action under Section 502(a) of ERISA if his or her claim is
            denied upon appeal.

<PAGE>

                  (c) In the case of a denial of a claim, a Claimant who wishes
            to appeal the decision shall follow the administrative procedures
            for an appeal as set forth in Section 3.6 below.

      2. The Section 3.6 is amended as follows:

            3.6 Appeals Procedures. A Claimant who wishes to appeal the denial
      of his or her claim for benefits shall follow the administrative
      procedures for an appeal as set forth in this Section and shall exhaust
      such administrative procedures prior to seeking any other form of relief.
      Appeals shall be reviewed in accordance with the procedures established by
      the Committee subject to the following administrative procedures set forth
      in this Section.

                  (a) In order to appeal a decision rendered with respect to his
            or her claim for benefits, a Claimant must file an appeal with the
            Committee in writing within 60 days following his or her receipt of
            the notice of denial with respect to the claim.

                  (b) The Claimant's appeal may include written comments,
            documents, records and other information relating to his or her
            claim. The Claimant may review all pertinent documents and, upon
            request, shall have reasonable access to or be provided free of
            charge, copies of all documents, records, and other information
            relevant to his or her claim.

                  (c) The Committee shall provide a full and fair review of the
            appeal and shall take into account all claim related comments,
            documents, records, and other information submitted by the Claimant
            without regard to whether such information was submitted or
            considered under the initial determination or review of the initial
            determination. Where appropriate, the Committee will overturn a
            notice of denial if it determines that an error was made in the
            interpretation of the controlling plan documents or if the Committee
            determines that an existing interpretation of the controlling plan
            documents should be changed on a prospective basis. In the event the
            Claimant is a subordinate, as determined by the Committee, to an
            individual conducting the review, such individual shall recuse
            himself or herself from the review of the appeal.

                  (d) The Committee shall furnish the Claimant with written or
            electronic notice of the decision rendered with respect to an appeal
            within 60 days following receipt by the Committee of the appeal
            unless the Committee determines that special circumstances require
            an extension of time for processing the appeal. In the event an
            extension is necessary, written or electronic notice of the
            extension shall be furnished to the Claimant prior to the expiration
            of the initial 60 day period. The notice shall indicate the special
            circumstances requiring an extension of time and the date by which a
            final decision is expected to be rendered. In no event

                                       2
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            shall the period of the extension exceed 60 days from the end of the
            initial 60 day period.

                  (e) In the case of a denial of an appeal, the written or
            electronic notice of such denial shall set forth (i) the specific
            reasons for the denial, (ii) references to the Plan provisions upon
            which the denial is based, (iii) a statement that the Claimant is
            entitled to receive, upon request and free of charge, reasonable
            access to, and copies of, all documents, records, and other
            information relating to his or her claim for benefits, and (iv) a
            statement of the Claimant's right to bring a civil action under
            Section 502(a) of ERISA.

      IN WITNESS WHEREOF, Allergan, Inc. hereby executes this Fourth Amendment
to the Allergan, Inc. Supplemental Executive Benefit Plan on this 18th day of
December, 2002.

ALLERGAN, INC.

By: /s/ Douglas Ingram
    -------------------------------------------------------
    Douglas Ingram
    Corporate Vice President, General Counsel and Secretary

                                       3<PAGE>
                                                                   EXHIBIT 10.21

                                    ALLERGAN

                                      2003

                              MANAGEMENT BONUS PLAN

                                  JANUARY 2003

January 2003
<PAGE>

PURPOSE OF THE PLAN

The Allergan, Inc. 2003 Management Bonus Plan (the "Plan") is designed to reward
eligible management-level employees for their contributions to providing
Allergan's stockholders increased value for their investment through the
successful accomplishment of specific financial objectives and individual
performance objectives.

PLAN YEAR

The Plan year runs from January 1, 2003 through December 31, 2003 for all
locations that have a fiscal year beginning January 1 and ending December 31.
For the international locations with fiscal years beginning December 1 and
ending November 1, the Plan year is December 1, 2002 to November 30, 2003.

ELIGIBILITY

All regular full-time and part-time employees of Allergan, Inc. and its
subsidiaries (the "Company") scheduled to work 20 or more hours per week in
salary grades 7E and above who are not covered by any other bonus or sales
incentive plan are eligible to participate in the Plan. Notwithstanding anything
in this Plan to the contrary, any individual shall not be eligible to
participate in the Plan if such individual (a) performs services for the Company
and is classified or paid as an independent contractor (regardless of his or her
classification for federal tax or other legal purposes) by the Company or (b)
performs services for the Company pursuant to an agreement between the Company
and any other person including a leasing organization. For the locations where
the Plan year is January 1, 2003 through December 31, 2003, the participants
must be employed on or before June 30, 2003; for the locations where the Plan
year is December 1, 2002 through November 30, 2003, the participants must be
employed on or before May 31, 2003. Participants must be actively employed by
the Company on the date bonuses are paid in order to be eligible to receive a
bonus. Participants who resign or are terminated for reasons other than those
noted below will receive no bonus.

Bonuses, if any, for participants who become eligible after the beginning of the
plan year, retire (defined as age 55 or over with at least 5 years of service),
become disabled, die or transfer into a position covered by another incentive
plan will be prorated. Bonuses, if any, for participants who are laid-off will
be prorated provided the participant was eligible for at least six months of the
Plan year. All proration will be based on the number of months of participation
in the Plan during the Plan year.

PERFORMANCE OBJECTIVES

Bonuses for Plan participants are based on both corporate performance and
individual performance in relation to pre-established objectives, as follows:

CORPORATE OBJECTIVES

-     EARNINGS PER SHARE--Corporate performance is measured in terms of
      Allergan, Inc.'s Earnings Per Share (EPS) performance. EPS is defined as
      net earnings from continuing operations as measured by Wall Street divided
      by the weighted average number of common and common equivalent shares on a
      diluted basis.

-     OPERATING INCOME--Operating Income compared to budget will be considered
      for allocation of bonus pools by Business Unit/Function. Operating Income
      is defined as Net Sales minus Cost of Goods minus Selling and General
      Administrative expenses minus Research & Development minus allocated
      corporate interest where applicable.

January 2003                                                     03 MBP Page -1-
<PAGE>

INDIVIDUAL OBJECTIVES

      Management Bonus Objectives (MBOs) are prepared by each participant and
      his or her supervisor at the beginning of the Plan year and may be
      modified throughout the year as necessary. Objectives should reflect major
      results and accomplishments to be achieved in order to meet short-and
      long-term business goals that contribute to increased stockholder value.
      MBOs are expressed as specific, quantifiable measures of performance in
      relation to key operating decisions for the participant's business unit,
      such as managing inventory levels, receivables, expenses, or payables;
      increasing sales; eliminating unnecessary capital expenditures, etc.

      At the end of the Plan year, the supervisor evaluates the participant's
      performance in relation to his or her objectives in order to determine the
      size of the bonus award, if any. A more detailed description of how the
      award is calculated is provided under "Individual Bonus Award
      Calculation."

BONUS POOL CALCULATION

The two components of this calculation are: Earnings Per Share; and Operating
Income.

BONUS POOL FUNDING - Bonuses are funded when the Company achieves the
                        threshold level of EPS performance. The level of bonus
                        funding is first determined by EPS performance as
                        outlined in the table below.

-     EARNINGS PER SHARE

<TABLE>
<CAPTION>
                               2003 EPS RANGE                 BONUS % OF TARGET
                               --------------                 -----------------
<S>                                                           <C>
                                   -$0.22                           45.5%
                                   -$0.20                           46.5%
                                   -$0.18                           48.5%
                                   -$0.16                           51.5%
                                   -$0.14                           55.0%
                                   -$0.12                           59.0%
                                   -$0.10                           64.0%
                                   -$0.08                           70.0%
                                   -$0.06                           76.5%
                                   -$0.04                           83.0%
                                   -$0.02                           91.0%
                                   Target                            100%
                                   +$0.02                          109.0%
                                   +$0.04                          117.0%
                                   +$0.06                          123.5%
                                   +$0.08                          130.0%
                                   +$0.10                          136.0%
                                   +$0.12                          141.0%
</TABLE>

            If actual EPS results fall between the performance levels shown
            above, bonuses will be prorated accordingly.

January 2003                                                     03 MBP Page -2-
<PAGE>

BONUS POOL DIFFERENTIATION BY BUSINESS UNIT/FUNCTION

-     OPERATING INCOME--The target bonus pool determined by EPS performance is
      modified for each business unit/function based on Operating Income results
      vs. budget. That is, a business unit that exceeds budget will receive a
      greater share of the total Company pool than a business unit that is below
      budget.

At the end of the year, the President and Chief Executive Officer of Allergan,
Inc. may recommend adjustments to the bonus funding levels to the Organization
and Compensation Committee (the "Committee") after consideration of key
operating results. When calculating EPS performance for purposes of this Plan,
the Committee has the discretion to include or exclude any or all of the
following items:

      -     extraordinary, unusual or non-recurring items

      -     effects of accounting changes

      -     effects of financing activities

      -     expenses for restructuring or productivity initiatives

      -     other non-operating items

      -     spending for acquisitions

      -     effects of divestitures

INDIVIDUAL BONUS AWARD CALCULATION

Target bonus awards are expressed as a percentage of the participant's year-end
annualized base salary. The target percentages vary by salary grade (see
Attachment No. 1).

A participant's actual bonus award may vary above or below the targeted level
based on the supervisor's evaluation of his or her performance in relation to
the predetermined MBOs. Each participant may receive from 0% up to 150% of his
or her target bonus amount. However, the total of all bonus awards given within
each business unit must total no more than 100% of the total bonus pool dollars
allocated to that business unit.

METHOD OF PAYMENT

Cash awards are paid following the close of the Plan year after the review and
authorization of bonuses by the Committee. Bonuses will be paid within 30 days
following management communication of the award, through the participant's
normal payroll channel. In the event of a Change in Control (as defined in
Attachment No. 2), bonuses will be paid within 30 days of the effective date of
the Change in Control.

CHANGE IN CONTROL

If a Change in Control occurs after the close of the Plan year and Company
performance supports bonus pool funding, participants will be paid a bonus based
on performance in relation to the EPS target.

If the Change in Control occurs during the Plan year, participants will be paid
a bonus prorated to the effective date of the Change in Control and EPS
performance will be deemed to be the greater of:
<PAGE>

      -     100% of the EPS target or

      -     the prorated actual year-to-date EPS performance

January 2003                                                     03 MBP Page -3-
<PAGE>

In either case, a participant's actual bonus may vary above or below the
targeted level according to the provisions outlined in "Individual Bonus Award
Calculation" above. Participants must be employed by the Company or its
successor on the effective date of the Change in Control in order to receive the
prorated payment, unless their employment is terminated for retirement, death,
disability or otherwise without cause. For purposes of this plan, "cause" shall
be limited to only three types of events: the willful refusal to comply with a
lawful, written instruction of the Board so long as the instruction is
consistent with the scope and responsibilities of the participant's position
prior to the Change in Control; dishonesty which results in a material financial
loss to the Company (or to any of its affiliated companies) or material injury
to its public reputation (or to the public reputation of any of its affiliated
companies); or conviction of any felony involving an act of moral turpitude.

GENERAL

Management reserves the right to define corporate performance and individual
performance and to review, alter, amend, or terminate the Plan at any time. This
Plan does not constitute a contract of employment and cannot be relied upon as
such. Any questions regarding this Plan should be directed to the Human
Resources department or the Vice President, Compensation. This Management Bonus
Plan document supersedes any previous document you may have received.

January 2003                                                     03 MBP Page -4-
<PAGE>

                                ATTACHMENT NO. 1

                                    ALLERGAN

                           2003 MANAGEMENT BONUS PLAN

                                  TARGET AWARDS

<TABLE>
<CAPTION>
                               SALARY GRADE                  TARGET BONUS*
                               ------------                  -------------
<S>                                                          <C>
                                    7E                             10%
                                    8E                             15%
                                    9E                             20%
                                   10E                             25%
                                   11E                             30%
                                   12E                             35%
                                   13E                             40%
                                   14E                             50%
                                   15E                             55%
</TABLE>

--------
* As a percentage of year-end base salary.

January 2003                                                     03 MBP Page -5-
<PAGE>

                                ATTACHMENT NO. 2
                          CHANGE IN CONTROL DEFINITION

"Change in Control" shall mean the following and shall be deemed to occur if any
of the following events occur:

                  (a) Any "person," as such term is used in Sections 13(d) and
14(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act") (a
"Person"), is or becomes the "beneficial owner," as defined in Rule 13d-3 under
the Exchange Act (a "Beneficial Owner"), directly or indirectly, of securities
of Allergan, Inc., a Delaware corporation ("Allergan") representing (i) 20% or
more of the combined voting power of Allergan's then outstanding voting
securities, which acquisition is not approved in advance of the acquisition or
within 30 days after the acquisition by a majority of the Incumbent Board (as
hereinafter defined) or (ii) 33% or more of the combined voting power of
Allergan's then outstanding voting securities, without regard to whether such
acquisition is approved by the Incumbent Board;

                  (b) Individuals who, as of the date hereof, constitute the
Board of Directors of Allergan (the "Incumbent Board"), cease for any reason to
constitute at least a majority of the Board of Directors, provided that any
person becoming a director subsequent to the date hereof whose election, or
nomination for election by Allergan's stockholders, is approved by a vote of at
least a majority of the directors then comprising the Incumbent Board (other
than an election or nomination of an individual whose initial assumption of
office is in connection with an actual or threatened election contest relating
to the election of the directors of Allergan, as such terms are used Rule 14a-11
of Regulation 14A promulgated under the Exchange Act) shall, for the purposes of
this Agreement, be considered as though such person were a member of the
Incumbent Board of Allergan;

                  (c) The consummation of a merger, consolidation or
reorganization involving Allergan, other than one which satisfies both of the
following conditions:

                        (1) a merger, consolidation or reorganization which
would result in the voting securities of Allergan outstanding immediately prior
thereto continuing to represent (either by remaining outstanding or by being
converted into voting securities of another entity) at least 55% of the combined
voting power of the voting securities of Allergan or such other entity resulting
from the merger, consolidation or reorganization (the "Surviving Corporation")
outstanding immediately after such merger, consolidation or reorganization and
being held in substantially the same proportion as the ownership in Allergan's
voting securities immediately before such merger, consolidation or
reorganization, and

                        (2) a merger, consolidation or reorganization in which
no Person is or becomes the Beneficial Owner directly or indirectly, of
securities of Allergan representing 20% or more of the combined voting power of
Allergan's then outstanding voting securities; or

                  (d) The stockholders of Allergan approve a plan of complete
liquidation of Allergan or an agreement for the sale or other disposition by
Allergan of all or substantially all of Allergan's assets.

Notwithstanding the preceding provisions of this Section, a Change in Control
shall not be deemed to have occurred if the Person described in the preceding
provisions of this Section is (1) an underwriter or underwriting syndicate that
has acquired the ownership of any of Allergan's then outstanding voting
securities solely in connection with a public offering of Allergan's securities,
(2) Allergan or any subsidiary of Allergan or (3) an employee stock ownership
plan or other employee benefit plan maintained by Allergan (or any of its
affiliated companies) that is qualified under the provisions of the Internal
Revenue Code of 1986, as amended. In addition, notwithstanding the preceding
provisions of this Section, a Change in Control shall not be deemed to have
occurred if the Person described in the preceding provisions of this Section
becomes a Beneficial Owner of more than the permitted amount of outstanding
securities as a result of the acquisition of voting securities by Allergan
which, by reducing the number of voting securities outstanding, increases the
proportional number of shares beneficially owned by such Person, provided, that
if a Change in Control would occur but for the operation of this sentence and
such Person becomes the Beneficial Owner of any additional voting securities
(other than through the exercise of options granted under any stock option plan
of Allergan or through a stock dividend or stock split), then a Change in
Control shall occur.

January 2003                                                     03 MBP Page -6-

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