<PAGE>

                                                                Exhibit 10.13(b)
                              EMPLOYMENT AGREEMENT
                              --------------------


     THIS EMPLOYMENT AGREEMENT is made and entered into effective this 8th day
of October, 1993, by and between Jane C.I. Hirsh (the "Employee") and COPLEY
PHARMACEUTICAL, INC. (the "Company"), a Delaware corporation.

                                  WITNESSETH:
                                  ----------

     WHEREAS, Employee is considered a key employee of the Company; and

     WHEREAS, Employee and the Company desire to enter into an Agreement to
provide for Employee's continuing employment with the Company;

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained, the parties hereto agree as follows:

     1.  EMPLOYMENT; DUTIES.  During the term of the Employment Period (as
         ------------------
defined in Section 2), and subject to the terms and conditions hereof, the
Company shall employ the Employee as Chairperson of the Board and Chief
Executive Officer, and Employee shall perform such duties for the Company as are
incident to such position, together with such other duties, consistent with
Employee's knowledge, experience and position with the Company, as she may be
reasonably requested to perform by the Company from time to time in connection
with such employment.

          Employee accepts such employment, and agrees to render the services
described herein and to devote her entire available business time, effort, skill
and attention to promote the best interests of the Company.

     2.  EMPLOYMENT PERIOD.  The term of this Agreement shall automatically
         -----------------
commence on the date on which at least a majority of the Company's outstanding
voting securities shall have been acquired pursuant to the transactions
contemplated by the Acquisition Agreement dated as of October 8, 1993, by and
among Hoechst Celanese Corporation, HCCP Acquisition Corporation and the
Company, and shall end on the date five (5) years after such date, unless sooner
terminated pursuant to Section 5 hereof.  Thereafter, this Agreement shall
automatically be renewed for successive periods of one (1) year, unless the
Company shall have given the Employee not less than six (6) months' written
notice of non-renewal and shall pay the Employee the Severance Payments (as
defined below) that would be payable if Employee's employment were terminated in
accordance with Section 5.4 hereof.  The term "Employment Period" shall mean the
period of the Employee's employment with the Company hereunder.

     3.  SALARY.  As compensation for the services to be rendered by Employee
         ------
during the Employment Period, the Company shall pay Employee the base annual
salary of $385,000 ("Base Salary"), payable periodically consistent with the
Company's normal payroll practices,

<PAGE>

                                                                Exhibit 10.13(b)

less such deductions and amounts to be withheld therefrom as may be required
under applicable law. The Base Salary may be increased from time to time as
agreed upon by the Company and Employee; provided, that in the sole discretion
of the Board of Directors, Employee shall be entitled to receive inflation and
merit increases determined in accordance with past practices.

     4.  OTHER BENEFITS AND TERMS OF EMPLOYMENT.  During the Employment Period,
         --------------------------------------
the following benefits and other terms of employment shall also apply:

          (A) EXPENSES.  The Company shall reimburse Employee for customary and
              --------
necessary expenses reasonably incurred by Employee in the course of performing
those duties which are incident to her position or which she has been requested
to perform by the Company, all in accordance with the Company's normal
reimbursement policies.

          (B) BONUS.  Employee shall receive such quarterly, annual or other
              -----
bonuses as may, from time to time, be approved by the Company's Board of
Directors, based upon various factors reviewed by the Board and based on the
achievement of the objectives determined by the Board.  Such bonuses are
entirely within the discretion of the Board.  Employee shall also participate in
such other incentive compensation programs, if any, as the Company may establish
for key executive employees.  In addition to the foregoing, the Company will
continue to maintain an annual bonus pool the size of which shall be determined
in accordance with past practice.  Employee shall be eligible to receive a bonus
from such bonus pool as determined by the Company's Board of Directors in its
discretion.

          (C) OPTIONS.  At the discretion of the Board of Directors, Employee
              -------
shall be eligible to receive periodic grants of stock options to purchase shares
of the Company's Common Stock.  Any options to be granted shall be subject to an
appropriate option agreement in the form normally used by the Company with
respect to its key employees.

         (D) INSURANCE, OTHER BENEFITS.  Employee shall participate (at the
             -------------------------
Company's expense) in employee health, hospitalization, disability, group-term
life, vacation, and other benefit programs on the same basis as that of other
Company executives.  In addition, Employee shall be entitled to such other
benefits as may be generally maintained or provided by the Company for the
benefit of other key executive employees.

     5.  TERMINATION.
         -----------

          5.1  GENERAL.  The Employment Period shall terminate prior to its
               -------
scheduled expiration set forth in Section 2 upon the earliest of the following:
(i) the Employee's death, (ii) a determination that Employee has become
disabled, as defined in Section 5.2, (iii) termination "for cause" under the
provisions of Section 5.3, or (iv) termination without cause as provided in
Section 5.4.

          5.2  DISABILITY.  Employee shall be regarded as "disabled" for
               ----------
purposes of this Agreement if she has been unable to render the services
required of her hereunder, in a manner consistent with past practice, for a
period of four (4) consecutive months or for any period in the

                                       2
<PAGE>

                                                                Exhibit 10.13(b)

aggregate of eight (8) months in any twelve (12) month period because of a
serious and continuing health impairment, which impairment will most likely
result in Employee's continued inability to render the services required of her
hereunder in a manner consistent with past practices; provided, however, that
thirty (30) days' prior notice of termination for disability shall be given to
Employee

     If the Employee dies during the Employment Period (without regard to the
Company's right to terminate this Agreement thereupon), or if the Company
exercises its right to terminate the Employee under this Section 5.2, then in
each such case the Employee or her estate shall be entitled to the same payments
and other benefits as are provided in the event of termination pursuant to
Section 5.4 (including without limitation the acceleration of Employee's stock
options as provided in Section 5.4).  In the case of death or disability, at the
Company's option the salary and benefit payment obligations of the Company may
be funded by insurance paid for by the Company.

     In the event that there should be any dispute between Employee and the
Company as to whether Employee is "disabled" within the meaning of this
Agreement or as to whether Employee has recovered from any such disability, such
matter shall be conclusively determined by the written report of a physician
acceptable to the Board and Employee, who shall set forth in his report the
nature and seriousness of the impairment suffered by Employee and the likely
effect of such impairment on Employee's future ability to render the services
required hereunder.  Employee agrees to submit to examination by any such
physician to the extent reasonably requested by the Board for the purpose of
ascertaining the extent of Employee's disability or recovery therefrom and the
parties agree that any determination with respect to Employee's disability may
be conclusively resolved in the sole judgment of the Board if Employee should
fail to comply with any reasonable request by the Board to submit to such an
examination.

          5.3  FOR CAUSE.  The Company may terminate the Employment Period and
               ---------
discharge Employee for cause upon giving thirty (30) days' (five (5) days in the
case of subparagraph (iv) below) prior written notice to Employee of such
termination.  Regardless of any broader definition of "cause" which might
otherwise apply under applicable law, the term "for cause" as used herein shall
be defined to include only one or more of the following grounds:  (i)
misappropriation by Employee of any material amounts of money or other assets or
property (tangible or intangible) of the Company; (ii) the Employee's willful
refusal to perform reasonable assignments given to Employee commensurate with
such Employee's status, functions or responsibilities as a key employee;
provided, that (a) such refusal is material and repetitive, and (b) the Employee
shall have been given reasonable notice and explanation of each refusal, and
reasonable opportunity to cure such refusal, and no cure has been effected
within a reasonable time after notice; (iii) conviction of Employee of a felony;
or (iv) a breach of any of the provisions of Section 6 hereof.

          5.4  AT THE ELECTION OF THE COMPANY FOR REASONS OTHER THAN FOR CAUSE.
               ---------------------------------------------------------------
The Company may terminate the Employee's employment hereunder at any time during
the term of this Agreement without cause by giving ninety (90) days' advance
written notice to the Employee of an election to terminate.

                                       3
<PAGE>

                                                                Exhibit 10.13(b)

     In the event the Company exercises its right to terminate the Employee
under this Section 5.4, the Company agrees to pay the Employee a lump sum
severance or termination payment of (i) the greater of (a) the Employee's
aggregate Base Salary for the remainder of the Employment Period from the date
of termination, and (b) two (2) year's Base Salary at the then current rate,
(ii) medical and other health insurance benefits for such two years; and (iii)
the pro rata portion of any bonus to which the Employee is otherwise entitled
(the "Severance Payments").  Such Severance Payments shall be payable on the
Employee's last date of employment hereunder and shall be subject to all
applicable federal and state withholding and other taxes.  In the event of a
termination under this Section 5.4, the Company may retain the Employee as a
consultant on terms mutually agreeable between the Company and the Employee.

     In addition, notwithstanding anything to the contrary contained in any
stock option agreement between the Employee and the Company, if the Company
exercises its right to terminate the Employee under this Section 5.4, then all
stock options then held by the Employee shall automatically accelerate and
become fully exercisable as of the date on which the Employee received notice of
termination.  Such stock options shall remain fully exercisable until the close
of business on the 60th day after the last date of the Employee's employment
with the Company hereunder.  The Company shall take any and all actions
necessary to effect the provisions of this paragraph.

     It shall be deemed to be a termination "without cause" if the Employee's
responsibilities and executive authority are reduced or diluted in any material
respect without the Employee's consent (which reduction or dilution is not
corrected by the Company within 30 days following written notification by
Employee to the Company that Employee intends to terminate her employment for
such reason), or the Employee is relocated to another Company office or facility
more than 25 miles from Canton, Massachusetts without the Employee's consent.

     In the event that Employee would, except for the remainder of this Section,
be subject to a tax pursuant to Section 4999 of the Internal Revenue Code of
1986, as amended, (the "Code") or any successor provision that may be in effect,
as a result of "parachute payments" (as that term is defined in Section
280G(b)(2)(A) and (d)(3) of the Code) made pursuant to this Agreement, or a
deduction would not be allowed to the Company for all or any part of such
payments by reason of Section 280G(a) of the Code, or any successor provision
that may be in effect, such payments shall be reduced, eliminated, or postponed
in such amounts as are required to reduce the aggregate "present value" (as that
term is defined in Section 280G(d)(4) of the Code) of such payments to one
dollar less than an amount equal to three times Employee's "base amount," (as
that term is defined in Section 280G(b)(3)(a) and (d)(1) and (2) of the Code) to
the end that Employee is not subject to tax pursuant to such Section 4999 and no
deduction is disallowed by reason of such Section 280G(a).  To achieve such
required reduction in aggregate present value, Employee in her sole discretion
shall determine what item(s) constituting the parachute payments shall be
reduced, eliminated or postponed, the amount of each such reduction, elimination
or postponement, and the period of each such postponement.  To enable Employee
to make such determine, the Company shall be required to provide Employee with
such information as is reasonably necessary for such determination.

                                       4
<PAGE>

                                                                Exhibit 10.13(b)

     Prior to the making of any payment under this Section, either party may
request a determination as to whether such payment would constitute a "parachute
payment," and, if so, the amount by which the payment must be reduced in
accordance herewith.  If such a determination is requested, it shall be made
promptly, at the Company's expense, by independent tax counsel selected by the
Employee and approved by the Company (which approval shall not unreasonably be
withheld), and such determination shall be conclusive and binding on the
parties.  The Company shall provide such information as such counsel may
reasonably request, and such counsel may engage accountants or other experts at
the Company's expense to the extent that they deem necessary or advisable to
enable them to reach a determination.

          5.5  EFFECT OF TERMINATION.  Notwithstanding any termination of the
               ---------------------
Employment Period, the Company shall promptly pay Employee any amounts due to
Employee with respect to all accrued but unpaid salary and accrued but unused
vacation time to the date of termination.  If Employee is deceased, such
payments shall be made to such individual or entity as Employee may have
designated in writing submitted to the Company or, in the absence of such
written designation, to Employee's estate.

     6.  COVENANTS OF THE EMPLOYEE.  In consideration of the Employee's
         -------------------------
continued employment with the Company, Employee hereby agrees that:

          6.1  NONCOMPETITION COVENANT.  During the Employment Period and for
               -----------------------
one additional year thereafter the Employee will not, whether alone or as a
partner, officer, director, consultant, principal, distributor, representative,
agent, employee or stockholder of any company or other commercial enterprise,
engage in any business or other commercial activity which is competitive with
the products, services being marketed, distributed or developed by the Company.
The foregoing prohibition shall not prevent employment or engagement by any
company or business organization not engaged in such business as long as the
activities of any such employment or engagement, in any capacity, do not involve
work on matters directly or indirectly related to the products, services or
strategy being developed, manufactured or marketed by the Company. Ownership of
less than five percent (5%) of the outstanding shares of a company whose stock
is publicly traded shall not be a violation of this provision. If the Employee
is terminated without "cause" (as defined herein), the provisions of this
Section 6.1 shall not apply unless the Company shall have promptly made the
payments required to be made by it pursuant to Section 5.4 hereof.

          6.2  NONSOLICITATION.  During the Employment Period and for one
               ---------------
additional year thereafter the Employee will not, directly or indirectly, either
for herself or for any other commercial enterprise, solicit, divert or take away
or attempt to solicit, divert or take away, any of the Company's customers,
business or prospective customers. For purposes of this Agreement, "prospective
customers" shall include those customers who have been solicited by the Company
within one year before the date Employee's employment with the Company
terminated. Furthermore, during such period, the Employee will not solicit any
employee of the Company for the employment of such Company employee by any
commercial enterprise, other than for the Company, nor recruit, solicit, attempt
to recruit or solicit, hire, or attempt to hire any

                                       5
<PAGE>

                                                                Exhibit 10.13(b)

such Company employee for any other commercial enterprise, whether or not such
enterprise may be a competitor of the Company.

          6.3  NONDISCLOSURE OBLIGATION.  The Employee will not at any time,
               ------------------------
whether during or after the term of this Agreement, and regardless of any early
termination thereof, for any reason whatsoever (other than to promote and
advance the business of the Company), reveal to any person or entity (both
commercial and non-commercial) any of the trade secrets, proprietary rights or
confidential business information concerning the Company, including but not
limited to its research and development activities, product designs, prototypes,
technical specifications, processes, formulae, inventions, methods and
memoranda, know-how and know-how, marketing plans and strategies, pricing and
costing policies, customer and supplier lists and accounts, and business,
finances or financial information of the Company so far as they have come and
may come to the Employee's knowledge, except as may be required in the ordinary
course of performing her duties as an Employee.  These restrictions shall not
apply to:  (i) information that may be disclosed generally or is in the public
domain through no default of the Employee; (ii) information received from a
third party who has not violated its own confidentiality obligation to the
Company; (iii) information approved for release by written authorization of the
Company; or (iv) information that may be required by law or an order of any
court, agency or proceeding to be disclosed.  The Employee shall keep secret all
matters of such nature entrusted to her and shall not use or disclose any such
information in any manner which causes loss to the Company.

          6.4  ASSIGNMENT OF INVENTIONS.  It is expressly understood and agreed
               ------------------------
that any and all right, title and interest of the Employee in any inventions,
discoveries and patent rights conceived or developed by the Employee during the
term of this Agreement (and thereafter if Employee remains an employee of the
Company) which relate to or arise out of her employment services rendered to the
Company are "works for hire" and are hereby assigned to the Company by the
Employee and shall be the sole and exclusive property of the Company.

          6.5  REFORMATION OF AGREEMENT.  In the event that any of the covenants
               ------------------------
contained in this Section 6 may be found by a court of competent jurisdiction to
be invalid or unenforceable as against public policy or otherwise, the parties
hereto expressly authorize such court to exercise its discretion in reforming
any such covenant to the end that Employee shall be subject to the greatest
extent permissible to confidentiality and noncompetition covenants that are
reasonable under the circumstances, enforceable by the Company, and consistent
with the Company's legitimate interests (acknowledged by the parties) in
protecting the Company's goodwill associated with the experience, skills, and
loyalty of Employee and with protecting the value of the business and assets of
the Company.

          6.6  INJUNCTIVE RELIEF.  In the event of a breach or threatened
               -----------------
breach by Employee of any of the covenants contained in this Section 6, Employee
agrees that the Company shall be entitled to injunctive relief in a court of
appropriate jurisdiction to remedy any such breach or threatened breach.

                                       6
<PAGE>

                                                                Exhibit 10.13(b)

     7.  INDEMNIFICATION.  The Company hereby agrees to indemnify Employee to
         ---------------
the maximum extent permitted by applicable law against all costs, charges, and
expenses incurred or sustained by her in connection with any action, suit, or
other proceeding to which she may be made a party by reason of her being an
employee of the Company or by reason of any action taken or omitted to be taken
in good faith by Employee in such capacity, to the extent that Employee's
actions or omissions are consistent with and not in breach of the provisions of
this Agreement.  The provisions of this Section 7 shall not be interpreted to
limit any right to indemnification that the Employee may have under the
Certificate of Incorporation or By-laws of the Company, by contract or otherwise
or under applicable law.

     8.  NONASSIGNABILITY.  This Employment Agreement may not be assigned by
         ----------------
either Company or Employee, except that the Company may assign its rights under
this Agreement to any affiliated corporation by means of assignment, merger, or
otherwise; and no such assignment shall impair the rights or obligations of the
parties as provided herein.

     9.  MISCELLANEOUS.
         -------------

         9.1  NOTICES.  All notices and other communications required or
              -------
permitted to be given hereunder shall be in writing and shall be deemed to have
been duly given when delivered by hand, sent by overnight courier service or
facsimile transmission, or dispatched by certified mail to the parties at the
following addresses or to such other address for a party as such party may have
designated to the other in a prior notice given in accordance herewith:

              (a)  If to the Company, to:

                   Copley Pharmaceutical, Inc.
                   25 John Road
                   Canton, MA  02021
                   Attn:  President

                   Fax: (617) 821-4068

                   with a copy of such notice to:

                   Leslie E. Davis, Esq.
                   Testa, Hurwitz & Thibeault
                   53 State Street
                   Boston, MA  02109

                   Fax:  (617) 248-7100

              (b)  If to Employee, to:

              Jane C.I. Hirsh
              c/o Copley Pharmaceutical, Inc.
              25 John Road
              Canton, MA  02021

                                       7
<PAGE>

                                                                Exhibit 10.13(b)



     9.2  ENTIRE AGREEMENT.  This Agreement sets forth the entire agreement and
          ----------------
understanding of the parties hereto concerning the subject matter hereof and
supersedes any prior understandings and agreements relating to the terms of the
Employee's employment by the Company.

     9.3  AMENDMENTS; WAIVERS.  This Agreement may be amended, modified,
          -------------------
superseded, or cancelled and the terms or covenants hereof may be waived, only
by a written instrument specifically referring to this Agreement and executed by
both of the parties hereto, or, in the case of a waiver, by the party entitled
to the benefit of such provision.  The failure of the Company at any time or
from time to time to require performance of any of Employee's obligations under
this Agreement shall in no manner affect the Company's right to enforce any
provisions of this Agreement at a subsequent time; and the waiver by the Company
of any right arising out of any breach shall not be construed as a waiver of any
right arising out of any subsequent breach.

     9.4  SEVERABILITY.  If any provision of this Agreement, or the application
          ------------
thereof to any person or circumstance, should, for any reason and to any extent,
be invalid or unenforceable, the remainder of this Agreement shall not be
affected thereby.

     9.5  GOVERNING LAW.  This Agreement shall be governed by and construed in
          -------------
accordance with the laws of the Commonwealth of Massachusetts applicable to
contracts made and to be performed entirely within such Commonwealth.

     9.6  HEADINGS.  The section headings contained in this Agreement are
          --------
intended solely for convenience of reference and shall be given no effect in the
construction or interpretation of this Agreement.



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                                       8
<PAGE>

                                                                Exhibit 10.13(b)

     IN WITNESS WHEREOF, the parties have duly executed this Agreement on the
date first written above, effective as of such date.


                             EMPLOYEE:




                             Jane C.I. Hirsh


                             COPLEY PHARMACEUTICAL, INC.


                             By:


                             Title:

                                       9