Exhibit 2.2

November 30, 2001


VIA HAND DELIVERY

DFB Pharmaceuticals, Inc.                     DPT Lakewood, Inc.
318 McCullough Street                         DFB Pharmaceuticals, Inc.
San Antonio, Texas  78215                     318 McCullough Street
                                              San Antonio, Texas  78215

West Pharmaceutical Services Lakewood, Inc.   Charter Laboratories, Inc.
c/o West Pharmaceutical Services, Inc.    c/o West Pharmaceutical Services, Inc.
101 Gordon Drive                              101 Gordon Drive
Lionville, PA 19341                           Lionville, PA 19341

Paco Laboratories, Inc.
c/o West Pharmaceutical Services, Inc.
101 Gordon Drive
Lionville, PA 19341

Re:   Amendments to the Asset Purchase Agreement

Gentlemen and Ladies:

The terms set forth in that certain Asset Purchase  Agreement (the "Agreement"),
dated  as  of  November  15,  2001,  by  and  among  DFB  Pharmaceuticals,  Inc.
("Parent"), DPT Lakewood, Inc. ("Buyer"), West Pharmaceutical Services Lakewood,
Inc. ("Lakewood"),  Charter Laboratories, Inc., Paco Laboratories, Inc. ("Paco")
(each of Lakewood,  Charter and Paco being hereinafter  individually referred to
as "Seller" and also collectively,  where applicable,  referred to as "Seller"),
and West Pharmaceutical Services, Inc. ("Stockholder") are hereby amended as set
forth below. Capitalized terms contained herein and not otherwise defined, shall
have the meanings  ascribed to them in the  Agreement.  Except as expressly  set
forth below, all terms and provisions of the Agreement are, and shall remain, in
full force and effect.

1.   Treatment of the Indenture and the  Debentures.  For all purposes under the
Agreement,   each  of  the  Indenture  and  the  Debentures  shall  be  Retained
Liabilities  and  shall no longer  be  included  in the  definition  of  Assumed
Liabilities.

2.   Definition  of  "Debentures".  The  definition  of  "Debentures"  is hereby
deleted and replaced in its entirety by the following:

""Debentures"  - the  Paco  Pharmaceutical  Services,  Inc.  6-1/2%  Convertible
Subordinated Debentures due March 1, 2007."


3.   Section 2.3.  Section 2.3 of the  Agreement  is hereby  revised by deleting
"$24,000,000"  appearing in the third line of such  paragraph  and  replacing it
with "$28,025,000".

4.   Section  2.4(a)(iv).  Section  2.4(a)(vi) is hereby deleted in its entirety
and replaced with the following:

          "(vi) intentionally omitted;"

5.   Section  2.4(b)(iv).  Section  2.4(b)(iv) is hereby deleted in its entirety
and replaced with the following:

          "(iv) any  Liability of Seller  arising out of or relating to Seller's
     credit  facilities,   the  Indenture  and  any  security  interest  related
     thereto;"

6.   Section  2.7(b)(i).   Section  2.7(b)(i)  is  hereby  revised  by  deleting
"$24,000,000"  appearing in the first line of such  paragraph  and  replacing it
with "$28,025,000".

7.   Section  2.7(b)(vi).  Section  2.7(b)(vi) is hereby deleted in its entirety
and replaced with the following:

          "(vi) intentionally omitted;"

8.   Section 2.8.  Section 2.8 is hereby amended by adding new subsection (c) to
the end of such Section:

"Notwithstanding  anything  set  forth in the  Agreement  to the  contrary,  the
Adjusted  Amount shall not be adjusted  (either  positively or negatively)  with
respect to any amount  attributable  to interest  arising under the Indenture or
the Debentures."

9.   Schedule  3.1(c).  Effective as of the Closing Date,  the last paragraph of
Schedule 3.1(c) shall be deleted in its entirety.

10.  Section 3.23.  Section 3.23 is hereby  deleted in its entirety and replaced
with the following:


"Section 3.23     Intentionally Omitted"

11.  Section  4.3(b).  Section  4.3(b) is hereby  deleted  in its  entirety  and
replaced with the following:

         "(b)     Intentionally Omitted."

12.  Section  11.2(e).  Section  11.2(e) is hereby  deleted in its  entirety and
replaced with the following:

         "(e)     intentionally omitted;"

13.  Schedule  11.2(e).  Schedule  11.2(e) is hereby  deleted  in its  entirety.
Intending to be legally bound hereby,  Stockholder  hereby  delivers this letter
pursuant to Section  13.4 of the  Agreement.  This letter may be executed in any
number of  counterparts.  The  provisions of this letter will be governed by and
construed  under the law of the State of New Jersey  without regard to conflicts
of law principles  that would require the  application of any other law.  Please
countersign   this  letter  in  the  space   provided  below  to  indicate  your
acknowledgement  of and  agreement to the terms set forth herein and your intent
to be legally bound hereby.

Very truly yours,

WEST PHARMACEUTICAL SERVICES, INC.



By:      /s/ John R. Gailey III
         Name:  John R. Gailey III
         Title:  Vice President and General Counsel

ACKNOWLEDGED AND AGREED:

DFB PHARMACEUTICALS, INC.


By:      /s/ Paul Johnson
         Name:  Paul Johnson
         Title:  Senior Vice President

DPT LAKEWOOD, INC.


By:      /s/ Paul Johnson
         Name:  Paul Johnson
         Title:  Senior Vice President and
                  General Manager

WEST PHARMACEUTICAL SERVICES LAKEWOOD, INC.


By:      /s/ Michael A. Anderson
         Name:  Michael A. Anderson
         Title:  President

CHARTER LABORATORIES, INC.


By:      /s/ Michael A. Anderson
         Name:  Michael A. Anderson
         Title:  President

PACO LABORATORIES, INC.


By:      /s/ Michael A. Anderson
         Name:  Michael A. Anderson
         Title:  President