EXHIBIT 2.1
                   FIRST AMENDMENT TO STOCK PURCHASE AGREEMENT
     This FIRST AMENDMENT TO STOCK PURCHASE AGREEMENT (this "Amendment") is made
and entered  into as of March 31,  1998,  by and among  COLUMBIA/HCA  HEALTHCARE
CORPORATION,  a Delaware corporation  ("Columbia"),  VH HOLDINGS, INC., a Nevada
corporation   ("Holdings"),   GALEN  HOLDINGS,   INC.,  a  Delaware  corporation
("Galen"), and EXPRESS SCRIPTS, INC., a Delaware corporation ("Purchaser").
                                    RECITALS:
     WHEREAS,  the parties  hereto have entered into that certain Stock Purchase
Agreement, dated as of February 19, 1998 (the "Original Agreement"); and
     WHEREAS, the parties wish to amend the Original Agreement;
     NOW,  THEREFORE,  in  consideration of the foregoing  premises,  the mutual
covenants  and  agreements  set  forth  herein,  and  other  good  and  valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereby agree as follows.
     1. DEFINITIONS.
     (a)  Capitalized  terms used herein but not otherwise  defined herein shall
have the meanings ascribed to such terms in the Original Agreement.
     (b) As used herein,  the following terms shall have the meanings  indicated
below, and where  appropriate  shall include the singular and plural of the term
defined:
     "Agreement" shall mean the Original Agreement as amended by this Amendment.
     "Amendment" shall mean this First Amendment to Stock Purchase Agreement.
     "Original  Agreement"  shall mean that certain  Stock  Purchase  Agreement,
dated as of February 19, 1998, by and among the parties to this Amendment.
     2.  AMENDMENT.  The Original  Agreement is hereby  amended in the following
respects:
     (a) Schedule  2.2(i) to the Original  Agreement is hereby amended by adding
the following  corporations to such schedule:  MedManagement  Holdings,  Inc., a
Nevada corporation, and Value Health Holdings, Inc., a Nevada corporation.
     (b) Section 3.1(b) of the Original Agreement is hereby deleted and replaced
in its entirety with the following Sections 3.1(b) and (c):
     "(b) Holdings is a corporation duly organized, validly existing and in good
standing  under  the Laws of the State of  Nevada.  Holdings  is a  wholly-owned
subsidiary of Columbia.
     (c) ▇▇▇▇▇ is a corporation  duly  organized,  validly  existing and in good
standing  under  the Laws of the  State  of  Delaware.  ▇▇▇▇▇ is a  wholly-owned
subsidiary of Columbia."
     Additionally, all references in the Original Agreement to ▇▇▇▇▇ as a Nevada
corporation are changed to reflect that ▇▇▇▇▇ is a Delaware corporation.
     (c) Section 9.4(a) of the Original Agreement is hereby deleted and replaced
in its entirety with the following Section 9.4(a):
     "(a) LIABILITY THRESHOLDS.  Notwithstanding  anything in this Article IX to
the contrary,  no  indemnified  Damages with respect to Claims  arising out of a
breach of Sellers' representations and warranties (other than Claims arising out
of a breach of the Title  Representations,  as such term is  defined  in Section
9.4(c)(i),  to which the Liability  Threshold  shall not apply) shall be payable
pursuant to this Article IX unless and until the aggregate amount of indemnified
Damages  asserted  against  Sellers  under this  Article IX with respect to such
Claims  equals or  exceeds  $2,600,000  (the  "LIABILITY  THRESHOLD").  Once the
Liability  Threshold for such Claims has been reached,  the Indemnitee  shall be
entitled to the benefit of the  indemnity  under this Article IX for such Claims
to the extent of any and all Damages  above the  Liability  Threshold;  provided
that the maximum amount of Damages for which Sellers shall be  responsible  with
respect to Claims  arising  out of  breaches  of  Sellers'  representations  and
warranties (including breaches of the Title  Representations) shall be an amount
equal  to  the  Purchase  Price.  For  purposes  of  calculating  the  Liability
Threshold,  Damages with respect to Claims  arising out of a breach of the Title
Representations  shall not be  counted  in  determining  whether  the  Liability
Threshold has been reached."
     (d) Section  9.4(c)(i)  of the  Original  Agreement  is hereby  deleted and
replaced in its entirety with the following Section 9.4(c)(i):
     "(i) The  representations  and warranties set forth in this Agreement shall
survive the Closing and shall expire  eighteen  months after the Effective Time;
provided  that  the   representations  and  warranties  set  forth  in  Sections
3.2(a)(iii),    3.2(a)(iv),   3.2(b)(iii),   3.2(b)(iv),   3.3(d)   and   3.3(e)
(collectively,  the "Title Representations") shall survive without limitation as
to time.  Except  with  respect  to the  Title  Representations,  no  claim  for
indemnification  arising out of a breach of such  representations and warranties
may be brought after that time."
     (e) Schedule 3.3 to the Original  Agreement is hereby  deleted and replaced
in its entirety with the form of Schedule 3.3 attached hereto as EXHIBIT A.
     (f)  Schedule  3.9 is hereby  amended  by adding  the  following  under the
heading "Pending Lawsuits Handled by Value Rx":
MATTER                    VENUE                TYPE         SUMMARY
-------------------------------------------------------------------------------
Sunergeo, Inc. v.        District Court of     Breach of    Complaint filed
Health Care Services,    ▇▇▇▇▇▇ County,        Contract     3/12/98, not served,
Inc. and ValueRx, Inc.   Texas                              alleging that 
                                                            ValueRx breached a
                                                            Prescription
                                                            Agreement by failing
                                                            to make payments due
                                                            February 10, 1998
                                                            and March 10, 1998
     (g) Schedule 3.10 is hereby  amended by adding the following as paragraph 2
thereof:
     "2. See Schedule 3.9  regarding  allegations  by  Sunergeo,  Inc.  that the
Company is in breach of a Prescription Agreement, dated August 26, 1992, between
Sunergeo and Health Care Services, Inc."
     (h)  Schedule  3.12(d) to the Original  Agreement is hereby  amended by (i)
changing  the  reference  to  "Schedule  3.12(b)" in such  schedule to "Schedule
3.12(d)," and (ii) attaching to such schedule the letters dated January 9, 1998,
and February 4, 1998 that are referred to in such schedule  (copies of which are
attached to this Amendment as EXHIBIT B).
     3. ADDITIONAL AGREEMENTS.
     (a) Notwithstanding the provisions of Section 2.4, the Effective Time shall
be 12:01 a.m., April 1, 1998.
     (b)  Columbia  shall  use all  reasonable  efforts  to assist  in:  (i) the
reinstatement  of ValueRx of Iowa,  Inc. as a corporation in good standing under
the laws of the State of Illinois as promptly as practicable; and (ii) obtaining
evidence of good  standing  and payment of franchise  taxes by the  corporations
identified in Exhibit C in the jurisdictions therein specified.
     4. MISCELLANEOUS.
     (a)  Except as  otherwise  specifically  set forth in this  Amendment,  the
Original  Agreement  remains in full  force and  effect,  without  modification,
amendment or change.
     (b) The  respective  representations  of the  parties set forth in Sections
3.4, 3.5, 4.2 and 4.3 of the Original Agreement shall apply to this Amendment.
     IN WITNESS  WHEREOF,  the parties have caused this First Amendment to Stock
Purchase Agreement to be executed as of the date first above written.
                                           COLUMBIA/HCA HEALTHCARE CORPORATION
     
                                            By:  /S/ V. ▇▇▇▇ ▇▇▇▇▇▇
                                            Name:  V. ▇▇▇▇ ▇▇▇▇▇▇
                                            Title:  VICE PRESIDENT
                                            VH HOLDINGS, INC.
                                            By:  /S/ V. ▇▇▇▇ ▇▇▇▇▇▇
                                            Name:  V. ▇▇▇▇ ▇▇▇▇▇▇
                                            Title:  VICE PRESIDENT
                                            ▇▇▇▇▇ HOLDINGS, INC.
                                            By:  /S/ V. ▇▇▇▇ ▇▇▇▇▇▇
                                            Name:  V. ▇▇▇▇ ▇▇▇▇▇▇
                                            Title:  VICE PRESIDENT
                                            EXPRESS SCRIPTS, INC.
                                            By:  /S/ ▇▇▇▇▇▇ ▇▇▇
                                            Name: ▇▇▇▇▇▇ ▇▇▇
                                            Title: SENIOR VICE PRESIDENT AND CFO
       List of Exhibits to the First Amendment to Stock Purchase Agreement
     1. Exhibit A -  Replacement  Schedule 3.3 to the Stock  Purchase  Agreement
listing all Value Health Subsidiaries.
     2.  Exhibit B - Two letters from ▇▇▇▇▇  ▇▇▇▇▇▇▇ of ▇▇▇▇▇▇▇▇  ▇▇▇▇▇▇▇ LLP to
the Internal Revenue Service regarding the Value Health, Inc. Retirement Savings
Plan
     3. Exhibit C - Listing of various Value Health, Inc. subsidiaries and their
respective jurisdiction of incorporation.