<PAGE>

EXHIBIT 10.25 FOURTH AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT

                               September 30, 2003

         This Fourth Amendment to Amended and Restated Credit Agreement is
entered into as of the date set forth above ("Amendment") by and among Kendle
International Inc., an Ohio corporation having its principal place of business
in Cincinnati, Ohio (the "Borrower"), Bank One, NA, a national banking
association, as Agent for the Lenders ("Agent"), and the Lenders identified
herein (the "Lender(s)"). This Amendment amends that certain Amended and
Restated Loan Agreement dated as of June 3, 2002 among Borrower, Agent and
Lenders, as amended pursuant to a First Amendment to Amended and Restated Loan
Agreement dated as of June 3, 2002, a Second Amendment to Amended and Restated
Loan Agreement dated as of March 28, 2003 and a Third Amendment to Amended and
Restated Loan Agreement dated as of May 14, 2003 (as amended, the "Loan
Agreement"). Capitalized terms used herein and not otherwise defined shall have
the respective meanings set forth in the Loan Agreement.

                             Statement of Amendment

         In consideration of their mutual agreements hereunder and under the
Loan Agreement, the Borrower, Lenders and the Agent hereby agree to amend the
Loan Agreement as follows:

Definitions. Section 1.1 of the Loan Agreement is amended by deleting the
definition of Fixed Charge Coverage Ratio and substituting therefore the
following:

                  "Fixed Charge Coverage Ratio" shall mean, as of any reporting
                  day, the ratio of (a) Consolidated EBITDA for the fiscal
                  quarter of the Borrower ending on, or most recently preceding,
                  such day, minus unfunded Consolidated Capital Expenditures for
                  such period, minus Consolidated Cash Dividends for such
                  period, minus Consolidated Stock Repurchases for such period,
                  to (b) the sum of (i) Consolidated Interest Expense for such
                  period, plus, (ii) Consolidated Scheduled Funded Debt Payments
                  for such period.

Financial Covenants. The Loan Agreement is amended by deleting paragraph (a) to
Section 7.18 in its entirety and substituting therefore the following new
paragraph (a) to Section 7.18:

Fixed Charge Coverage Ratio. Borrower shall not permit its Fixed Coverage Ratio,
as of the last day of any fiscal quarter of Borrower, to be less than (i) 1.1 to
1.0 for the fiscal quarters ending on or about September 30, 2003, December 21,
2003 and March 31, 2004 and (ii) 1.2 to 1.0 for each fiscal quarter ending on or
about June 30, 2004 and thereafter. The severance charge in the amount of
approximately $850,000 incurred by Borrower and/or its Subsidiaries during the
fiscal quarter ended September 30, 2003 shall be excluded from the calculation
of the Fixed Charge Coverage Ratio for the fiscal quarter ended September 30,
2003.

Reaffirmation of Covenants, Warranties and Representations; Waiver. Borrower
hereby agrees and covenants that all representations and warranties in the Loan
Agreement are true and accurate in all material respects as of the date hereof.
Borrower further reaffirms all covenants in the Loan Agreement as if more fully
set forth herein. Conditions Precedent. Except as otherwise noted, as a
condition to the effectiveness of this Amendment, the following condition(s)
shall be satisfied:

Delivery to Agent of a certificate of the Secretary or Assistant Secretary of
Borrower (as to which Certificate there shall be no personal, as opposed to
corporate, liability) which will (A) certify the names of the officers of
Borrower authorized to sign this Amendment and any other documents or
certificates to be delivered pursuant to this Amendment by Borrower or any of
its officers together with the true signatures of such officers and (B) contain
copies of the resolutions of the Board of Directors of the Borrower authorizing
the execution, delivery and performance of the Borrower's obligations under
Amendment; and Payment to the Agent, for the ratable benefit of the Lenders, of
a modification fee in the aggregate amount of $6,000, payable on the date of
this Amendment.

Claims and Release of Claims by Borrower. The Borrower represents and warrants
that it has no claims, counterclaims, setoffs, actions or causes of actions,
damages or liabilities of any kind of nature whatsoever whether

<PAGE>

at law or in equity, in contract or in tort, whether now accrued or hereafter
maturing (collectively, "Claims") against Agent or Lenders, any direct or
indirect parent corporation or any direct or indirect affiliates of such parent
corporations, or any of the foregoing's respective directors, officers,
employees, agents, attorneys and legal representatives, or the heirs,
administrators, successors or assigns of any of them (collectively, "Lender
Parties"), that directly or indirectly arise out of, are based upon or are in
any manner connected with any Prior Related Event (as defined below). As used
herein, the term "Prior Related Event" means any transaction, event,
circumstance, action, failure to act, occurrence of any sort or type, whether
known or unknown, which occurred, existed, was taken, permitted or begun at any
time prior to the date of this Amendment or occurred, existed, was taken, was
permitted or begun in accordance with, pursuant to or by virtue of any of the
terms of the Loan Documents or any documents executed in connection with the
Loan Documents or which was related to or connected in any manner, directly or
indirectly to the extension of credit represented by the Loan Documents.

Representations, Warranties and Covenants. The Borrower represents, warrants and
covenants to the Agent and Lenders (which representations, warranties and
covenants shall survive the execution and delivery of this Amendment) as
follows:

The execution, delivery and performance of this Amendment have been duly
authorized by all necessary corporate actions on the part of the Borrower; and
No default exists under the Loan Agreement after giving effect to the foregoing
Amendment. Borrower shall pay all reasonable costs and expenses (including legal
fees and expenses) incurred by Agent and Lenders in connection with the
preparation of this Amendment. Confirmation of Loan Agreement. The Loan
Agreement, as amended by this Amendment, shall be read, taken and construed as
one and the same instrument, respectively. Except as amended and supplemented by
this Amendment, the terms and provisions of the Loan Agreement shall remain in
full force and effect.

         IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart
of this Amendment to be duly executed and delivered as of the date first above
written.

                                               KENDLE INTERNATIONAL INC.
                                       an Ohio corporation

                                       By:
                                          Karl Brenkert, III
                                          Senior Vice President

BANK ONE, NA                           KEYBANK NATIONAL ASSOCIATION
Lender and in its capacity as Agent

By:                                    By:
Name:                                  Name:
Title:                                 Title: