Exhibit 10.56

                               FIRST AMENDMENT TO
                             POST-CLOSING AGREEMENT

      This First Amendment to Post-Closing Agreement (this "First Amendment"),
is executed on the respective dates set forth below effective as of December 20,
2003 (the "Effective Date"), and is entered into by and among Drew Scientific,
Inc., Texas corporation ("Borrower "), Keith Drew, individually ("Drew"), Drew
Scientific Group, PLC, a public limited company organized under the laws of
England and Wales ("Drew PLC"), and Texas Mezzanine Fund Inc., a Texas
corporation ("Lender") for the purpose of amending and modifying that certain
Post-Closing Agreement executed as of November 20, 2003 (the "Original
Agreement"). Borrower, Drew, Drew PLC and Lender are collectively referred to
herein as the "Parties". All capitalized terms used in this First Amendment and
not otherwise defined herein shall have the meanings assigned to such terms in
the Original Agreement, unless the context specifically requires otherwise

                                    RECITALS

      A.    Pursuant to Section 2 of the Original Agreement, Drew was required
            to deliver to Lender, on or prior to the Effective Date, all of the
            Shares owned by Drew;

      B.    As of the Effective Date, Lender had received share certificates
            issued by Drew PLC to Drew evidencing ownership of 2,600,000 Shares;

      C.    Since the Effective Date, Lender has received share certificates
            issued by Drew PLC to Drew evidencing ownership of an additional
            573,984 Shares;

      D.    Drew has determined that he does not control Selbourne Limited
            ("Selbourne"), either directly or indirectly, and cannot either (i)
            pledge or cause the pledge of the 1,400,000 shares of Drew PLC
            issued to Selbourne ("Selbourne Shares") or (ii) cause to be
            delivered to Lender certificates evidencing such shares;

      E.    It has been determined that Paragraph 5a that the Original Agreement
            incorrectly slated the number of shares of Drew PLC of which Drew is
            the lawful owner as being 3,178,984 and that the correct number is
            3,173,984;

      F.    The Parties desire to correct the typographical error referenced in
            Recital D; and

      G.    The Parties desire to clarify that (since Drew does not own such
            shares) the Selbourne Shares are not collateral for the Loan and
            that certificates evidencing such shares need not be delivered to
            Lender.



                                    AGREEMENT

      NOW THEREFORE, in consideration of the premises and the mutual agreements
contained herein, the parties agree to amend the Original Agreement on the
following terms and conditions:

      1.    Delivery of Shares. There is hereby added at the end of Paragraph 2
of the Original Agreement the following:

            Notwithstanding the foregoing, if certificates have not been issued
            by Drew PLC to evidence any portion of the Shares, failure to
            deliver such Shares shall not constitute a default under this
            Paragraph.

      2.    Shares Owned; Selbourne Shares. Section 5(a) of the Original
Agreement is hereby amended to in its entirety to read: "Drew is the lawful
owner of record of 3,173,984 shares of Drew PLC".

      3.    Representation and Warranty. Section 6 of the Original Agreement is
hereby amended by adding a new Subsection 5.1 that reads as follows:

            Drew hereby represents and warrants that he has determined that he
            does not control Selbourne Limited ("Selbourne"), either directly or
            indirectly, and cannot either (i) pledge or cause the pledge of the
            1,400,000 shares of Drew PLC issued to Selbourne ("Selbourne
            Shares") or (ii) cause to be delivered to Lender certificates
            evidencing such shares.

      4.    Limitation. Except as expressly modified and amended by this First
Amendment, the terms, conditions and provisions of the Original Agreement shall
remain in full force and effect in all respects.

      5.    Counterparts. The Parties may execute this First Amendment in any
number of counterparts. Each such counterpart shall be deemed to be an original,
but all such counterparts shall together constitute one and the same agreement.

      6.    Amendment And Waiver. No amendment of this First Amendment, and no
waiver of any one or more of the provisions hereof shall be effective unless set
forth in a writing and signed by the parties hereto.

      7.    Governing Law. This First Amendment shall be governed by and
construed in accordance with the internal laws of the State of Texas without
reference to conflict of law principles.

      8.    Severability. Any provision of this First Amendment that is held to
be inoperative, unenforceable, voidable or invalid in any jurisdiction shall, as
to that jurisdiction, be ineffective, unenforceable, void or invalid without
affecting the remaining provisions in that or



any other jurisdiction, and to this end the provisions of this First Amendment
are declared to be severable.

      IN WITNESS WHEREOF, the parties hereto have executed this First Amendment
effective as of the date first above written.

                                        BORROWER:

                                        DREW SCIENTIFIC, INC.,
                                        a Texas corporation

Mar 8 '04                               By: /s/ K.R. DREW
- ----------------                            -------------------------
Date signed                             Name: K.R. DREW
                                        Title: President.

                                        DREW:

Mar 8 '04                               /s/ Keith Drew
- ----------------                        -----------------------------
Date signed                             Keith Drew, individually

                                        DREW PLC:

                                        DREW SCIENTIFIC GROUP, PLC
                                        a public limited company organized under
                                        the laws of England and Wales.

Mar 8 '04                               By: /s/ K.R. DREW
- ----------------                            -------------------------
Date signed                             Name: K.R. DREW
                                        Title: President

                                        LENDER:

                                        TEXAS MEZZANINE FUND, INC.,
                                        a Texas corporation

                                        By:
                                            -------------------------------
                                        Name:
- ----------------------                        -----------------------------
Date signed                             Title:
                                               ----------------------------