Document:

Exhibit 4.37

                                  Leonard Osser
                               110 E. 71st Street
                               New York, NY 10021

                                                              March 29, 2002

Milestone Scientific Inc.
220 South Orange Avenue
Livingston, NJ 07039
Attn: Thomas Stuckey-Chief Financial Officer

            RE:   Milestone Scientific Inc.
                  9% Secured Promissory Note

Dear Sirs:

      Please be advised that I hereby agree to defer until January 2, 2003 the
payment of all principal and interest owed to me under the Milestone Scientific
Inc. 9% Secured Promissory Note issued to me in April 2000.

                                                             Very truly yours,

                                                              Leonard OsserExhibit 4.38

                     SECOND AMENDMENT OF PURCHASE AGREEMENT
                             DATED JANUARY 31, 2000

      AMENDMENT, dated April 15, 2002, (the "Amendment") among Milestone
Scientific Inc., a Delaware corporation with its principal offices at 220 South
Orange Avenue, Livingston, New Jersey 07039 (the "Company"), and the holders of
the Company's 20% Senior Secured Promissory Notes (the "Notes") (individually,
the "Noteholder" and collectively, the "Noteholders") to Purchase Agreement
dated January 31, 2000.

                                    RECITALS

      WHEREAS, pursuant to an Amendment To Purchase Agreement, dated March 16,
2001 among the Company and the Noteholders (the "the Original Amendment" and
"Agreement", respectively), each Noteholder was issued by the Company a 20%
Senior Secured Promissory Note on which, as of March 31, 2002, there is a
balance in the amounts set forth opposite each Noteholder's name on Schedule A;

      WHEREAS, pursuant to paragraph 12.11 of the Agreement, the payment of
interest, time of payment of interest, the interest rate payable, payment of
principal and time of payment of principal on the Notes may be changed by the
written consent of holders then holding at least 80% of the outstanding
principal amount of the Notes; and

      WHEREAS, the Company and the undersigned Noteholders desire to amend the
Original Amendment and exchange their Notes for the Company's 6%/12% Senior
Secured Promissory Notes (the "New Notes") as described herein;

      NOW, THEREFORE, in consideration of the promises set forth below and other
good and valuable consideration, the sufficiency of which is hereby
acknowledged, the undersigned hereby agree as follows:

      1. The Company shall issue to each Noteholder a New Note having the
following terms:

      a.    The issuance date shall be as of March 31, 2002 (the "Issuance
            Date");

      b.    The maturity date shall be July 1, 2003 (the "Maturity Date");

      c.    The face value shall be equal to the outstanding principal and
            interest on the Noteholder's Note as of March 31, 2002 (the "Face
            Value");

      d.    Interest shall accrue on the Face Value at the rate of 6% per annum
            from the Issuance Date to the Maturity Date, if paid in cash, or 12%
            per annum

<PAGE>

            from the Issuance Date to the Maturity Date, if paid in Common
            Stock, as defined below. Interest shall be payable on the Maturity
            Date;

      e.    At the option of the Company, the Face Value shall be payable either
            in cash or in shares of the Company's Common Stock, Par value $.001
            per share (the "Common Stock"), valued at the average closing price
            per share of the Common Stock for the five trading days ending the
            day prior to the Maturity Date of the New Notes, provided that such
            shares of Common Stock have been registered pursuant to the
            Registration Rights Agreement among the Company and Noteholders,
            dated January 31, 2000 (the "Registration Rights Agreement");

      f.    The New Notes shall continue to be secured by raw material, work in
            process, finished goods inventories and certain proceeds thereof,
            copyrights, trademarks and other intellectual property that may now
            or hereinafter be owned by the Company, and the Company shall
            execute and deliver such documents and instruments and take other
            reasonable actions to insure that the Noteholders have a perfected
            first security interest in the above mentioned assets, all pursuant
            to the Security Agreement dated January 31, 2000 among the Company
            and the Noteholders (the "Security Agreement"), which is hereby
            amended to substitute the New Note for the Note in all references;

      g.    The payment of the entire Face Value, including all accrued
            interest, of the New Notes, shall be senior in right of payment to
            all other indebtedness of the Company, whether incurred prior or
            subsequent to the date of thereof other than (i) any purchase money
            obligations incurred by the Company in connection with the purchase
            of property in the ordinary course of business, and (ii) all payment
            obligations of the Company pursuant to any capitalized lease entered
            into by the Company, and (iii) all payables incurred by the Company
            in the ordinary course of its business; and

      h.    It is confirmed that there are no restrictions on the Company's
            right to obtain additional unsecured loans so long as they bear a
            maturity date that is subsequent to August 1, 2003.

      i.    Except as otherwise provided herein, the provisions of the Note
            relating to the rights of the Noteholders and the obligations of the
            Company shall be incorporated into the New Notes, which shall appear
            substantially in the form annexed hereto as Exhibit A.

      2. Each Noteholder shall promptly return his Notes to the Company in
exchange for the New Notes in the amount set forth opposite his name on Schedule
A.

      3. The Company's obligations and the rights of the Noteholders under the
Notes shall terminate upon the execution of this Amendment by the holders of 80%
of the

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<PAGE>

outstanding principal amount of the Notes, except for the right of the
Noteholders to exchange his Note for the New Note, as provided herein.

      4. As additional consideration for the extension of the maturity dates on
the Notes, the Company shall issue, to each of the undersigned Noteholders who
execute and return this Amendment to the Company by the close of business on
April 15, 2002, shares of the Company's Common Stock with a value of $120 for
each $1,000 Face Value of the New Note held by such Noteholder. The shares shall
be issued promptly following maturity and will be valued at the average closing
price during the five trading days preceding maturity.

      5. The Registration Rights Agreement is hereby amended to include in the
definition of "Registrable Securities" as used therein any shares of Common
Stock that may be issued as payment on principal and interest on the New Notes.

      6. Except as otherwise provided herein, the Agreement, the Security
Agreement, the Warrants, and the Registration Rights Agreement shall continue
unchanged and in full force and effect.

      IN WITNESS WHEREOF, the undersigned have caused this Amendment to be
executed as of the date first above written.

                                 MILESTONE SCIENTIFIC INC.

                                 By: ___________________________________________
                                       Leonard Osser, Chairman and
                                       Chief Executive Officer

                                 _______________________________________________
                                       K. TUCKER ANDERSEN

                                 CUMBERLAND PARTNERS
                                 by Cumberland Associates LLC, as its investment
                                 advisor

                                 By: ___________________________________________

                                       3
<PAGE>

                                 LONGVIEW PARTNERS

                                 by Cumberland Associates LLC, as its investment
                                 advisor

                                 By: ___________________________________________

                                 LONGVIEW PARTNERS B, L.P.
                                 by Cumberland Associates LLC, as its investment
                                 advisor

                                 By: ___________________________________________

                                 LONGVIEW PARTNERS C, L.P.
                                 by Cumberland Associates LLC, as its investment
                                 advisor

                                 By: ___________________________________________

                                 MORSE, ZELNICK, ROSE & LANDER

                                 By: ___________________________________________
                                               Stephen A. Zelnick

                                 _______________________________________________
                                               LEONARD OSSER

                                 STRATEGIC RESTRUCTURING
                                   PARTNERSHIP LP

                                 By: ___________________________________________
                                               Richard Haydon

                                       4
<PAGE>

                                 _______________________________________________
                                                   MITCHELL KUHN

                                 _______________________________________________
                                                   EDWARD SCHWARZ

                                 _______________________________________________
                                                   SARAH JANE JELIN

                                 _______________________________________________
                                                     JAY NELSON

                                 _______________________________________________
                                                  KEITH MICHAEL JEREB

                                 TRICOR SYSTEMS INCORPORATED

                                 By: ___________________________________________
                                                    Jack Jereb

                                 _______________________________________________
                                                  DANIEL BURACK

                                 _______________________________________________
                                                DAVID BIRKENRUTH

                                       5
<PAGE>

                                   SCHEDULE A

Noteholder                                                Face value of New Note

K. TUCKER ANDERSEN                                               $130,424.35

CUMBERLAND PARTNERS
by Cumberland Associates LLC,
as its investment advisor                                         130,461.25

LONGVIEW PARTNERS
by Cumberland Associates LLC,
as its investment advisor                                          14,495.69

LONGVIEW PARTNERS B, L.P.
by Cumberland Associates LLC,
as its investment advisor                                          18,759.13

LONGVIEW PARTNERS C, L.P.
by Cumberland Associates LLC,
as its investment advisor                                           6,821.50

MORSE, ZELNICK, ROSE
  & LANDER LLP                                                    111,529.13

LEONARD OSSER                                                     341,988.65

STRATEGIC RESTRUCTURING
  PARTNERSHIP LP                                                   21,447.60

MITCHELL G. KUHN                                                   41,938.90

EDWARD SCHWARZ and
  SARAH JANE JELIN                                                 45,242.49

JAY NELSON                                                       $ 36,263.54

                                       6
<PAGE>

KEITH MICHAEL JEREB                                                 9,065.89

TRICOR SYSTEMS
  INCORPORATED                                                     22,664.71

DANIEL BURACK                                                      45,242.49

DAVID BIRKENRUTH                                                   45,242.49

                                       7

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