Agreement to Incorporate Defined Terms - Astra AB, Merck & Co. Inc, Astra Merck Inc., Astra USA Inc., KB USA LP, Astra Merck Enterprises, Merck Holdings Inc. and Astra Pharmaceuticals LP




                     AGREEMENT TO INCORPORATE DEFINED TERMS

         AGREEMENT TO INCORPORATE DEFINED TERMS, dated as of June 19, 1998,
between ASTRA AB, a company limited by shares organized and existing under the
laws of Sweden ('Astra'), MERCK & CO., INC., a New Jersey corporation ('Merck'),
ASTRA MERCK INC., a Delaware corporation ('AMI'), ASTRA USA, INC., a New York
corporation and an indirect wholly-owned subsidiary of Astra ('Astra USA'), KB
USA, L.P., a Delaware limited partnership of which Astra is the general partner
and Astra USA is the limited partner ('KBUSALP'), ASTRA MERCK ENTERPRISES INC.,
a Delaware corporation and a direct wholly-owned subsidiary of AMI
('Enterprises'), KBI SUB INC., a Delaware corporation and a wholly-owned
subsidiary of AMI ('KBI Sub'), MERCK HOLDINGS, INC., a Delaware corporation and
a wholly-owned subsidiary of Merck ('Merck Holdings'), and ASTRA
PHARMACEUTICALS, L.P., a Delaware limited partnership (the 'Partnership').

                                   WITNESSETH:

         WHEREAS, Astra and Merck desire to restructure their joint venture
through the entry into the Partnership Agreement by KBUSALP and KBI Sub and the
modification and making of certain other contractual arrangements, as provided
in the Initial Agreements, the Ancillary Agreements and the Partnership
Agreement (such agreements being herein referred to as the 'Agreements') and, in
furtherance thereof, the parties hereto are entering into this agreement as of
the date hereof;

         WHEREAS, in order to insure the confidentiality of the negotiations
between the parties, the Agreements have been prepared using certain code words
as defined terms to disguise the true identity of the parties;

         WHEREAS, in order to expedite the preparation of execution copies of
the Agreements, such code words and related defined terms have been retained in
such execution copies; and

         WHEREAS, Astra, Merck, AMI, Astra USA, KBUSALP, Enterprises, KBI Sub,
Merck Holdings and the Partnership wish to sign such execution copies of the
Agreements and intend to give them binding effect and in connection therewith
have agreed to enter into this agreement which identifies the code words used as
defined terms in the Agreements and provides for the incorporation by reference
herein of such defined terms in each of the Agreements.

         NOW, THEREFORE, in consideration of the premises and the
representations, warranties and agreements contained in the Agreements, Astra,
Merck, AMI, Astra USA, KBUSALP, Enterprises, KBI Sub, Merck Holdings and the
Partnership hereto hereby agree as follows:

         1. The following defined terms used in the Agreements have the
following meanings:

                  'KB' means 'Astra' or 'Astra AB', as appropriate under the
circumstances.

                  'TR' means 'Merck' or 'Merck & Co., Inc.', as appropriate
under the circumstances.

                  'KBI', 'KB TR Inc.' or 'KBI TR Inc.' means 'Astra Merck' or
'Astra Merck Inc.', as appropriate under the circumstances

                  'KB USA' means 'Astra USA' or 'Astra USA, Inc.' as appropriate
under the circumstances.

                  'KBI Sub' means 'KBI Sub Inc.'

                  'KBLP' means 'KB USA, L.P.'

                  'KBI-E', 'KBI TR E' or 'KB TR Enterprises Inc.' means 'Astra
Merck Enterprises' or 'Astra Merck Enterprises Inc.', as appropriate under the
circumstances

                  'TR Holdings' means 'Merck Holdings' or 'Merck Holdings,
Inc.', as appropriate under the circumstances.

                  'KBI-P' means 'Astra Merck Pharmaceuticals' or 'Astra Merck
Pharmaceuticals, Inc.', as appropriate under the circumstances

                  'KB Pharmaceuticals, L.P.', the 'Partnership' or 'LP' means
'Astra Pharmaceuticals, L.P.'

                  Notwithstanding anything to the contrary herein, references to
'KB USA, L.P.' shall mean 'KB USA, L.P.'

         2. The foregoing defined terms shall be deemed incorporated by
reference in each of the Agreements.

         3. Terms used herein which are not defined shall have the meanings set
forth in the Master Restructuring Agreement dated as of the date hereof among
the parties hereto.

         4. The references on the signature pages of the Agreements to the
various parties thereto shall be deemed to mean the legal entities as herein
identified and by their execution of the Agreements and this agreement intend to
be fully legally bound thereby.


                                       2

         IN WITNESS WHEREOF, the parties have caused this agreement to be duly
executed as of the date first above written.

ASTRA AB                                MERCK & CO., INC.
     (publ)

By /s/ Goran Lerenius                   By /s/ Judy C. Lewent
   Name: Goran Lerenius                    Name: Judy C. Lewent
   Title: Authorized Signatory             Title: Senior Vice President and
                                                  Chief Financial Officer

ASTRA USA, INC.                         MERCK HOLDINGS, INC.

By /s/ Christian Onfelt                 By /s/ Peter E. Nugent
   Name: Christian Onfelt                  Name: Peter E. Nugent
   Title:Vice President                    Title: Authorized Signatory

ASTRA MERCK INC.                        KBI SUB INC.

By /s/ Peter E. Nugent                  By /s/ Peter E. Nugent
   Name: Peter E. Nugent                   Name: Peter E. Nugent
   Title: President                        Title: President

KB USA, L.P.                            ASTRA MERCK ENTERPRISES
                                        INC.

By: ASTRA AB, its General Partner
     (publ)
                                        By /s/ Peter E. Nugent
                                           Name: Peter E. Nugent
/s/ Christian Onfelt                       Title: President
Name: Christian Onfelt
Title: Authorized Signatory

                    ASTRA PHARMACEUTICALS, L.P.

                    By: KB USA, L.P., its General Partner

                    By: ASTRA AB, its General Partner
                         (publ)

                    /s/ Goran Lerenius
                    Name: Goran Lerenius
                    Title: Authorized Signatory