Exhibit 5.1

                       BRENMAN BROMBERG & TENENBAUM, P.C.
                        1775 Sherman Street, Suite 1001
                             Denver, CO 80203-4314
                              Phone (303) 894-0234
                               Fax (303) 839-1633


                                 April 30, 1998

The Board of Directors
Entropin, Inc.
45926 Oasis Street
Indio, CA 92201

Re:      Form SB-2 Registration Statement
         Opinion of Counsel

Dear Sirs:

         As  securities  counsel for Entropin,  Inc. (the  "Company") a Colorado
corporation,  we have examined the  originals or copies,  certified or otherwise
identified,  of the Articles of  Incorporation,  as restated  and  amended,  and
Bylaws of the Company,  corporate records of the Company, including minute books
of the  Company  as  furnished  to us by the  Company,  certificates  of  public
officials and of  representatives  of the Company,  statutes and other  records,
instruments and documents  pertaining to the Company as a basis for the opinions
hereinafter expressed. In giving such opinions, we have relied upon certificates
of officers of the Company with  respect to the accuracy of the factual  matters
contained in such certificates.

         We have also, as such counsel,  examined the Registration  Statement on
Form SB-2, File No. 333-_______ (the "Registration  Statement") to be filed with
the  Commission  on or about May 4, 1998  covering the resale of up to 5,934,547
shares of Common  Stock of the  Company  by the  Selling  Shareholders,  and the
Company's  issuance  of up to 180,001  shares of Common  Stock upon  exercise of
options, all as more particularly described in the Registration Statement.

         Based upon the  foregoing and subject to the other  qualifications  and
limitations stated in this letter, we are of the opinion that:

         (1)      The  outstanding  shares  of  Common  Stock  to be sold by the
                  Selling Shareholders have been duly authorized and are validly
                  issued, fully paid and non-assessable.

         (2)      The  shares of Common  Stock to be  issued to  holders  of the
                  options  held by the Selling  Shareholders,  and the shares of
                  Common Stock underlying the options, upon exercise and payment
                  of the  exercise  price  stated  therein,  will have been duly
                  authorized, validly issued, fully paid and non-assessable.

     This  opinion is a legal  opinion and not an opinion as to matters of fact.
This opinion is limited to the laws of the State of Colorado and the federal law
of the United States of America,  and to the matters stated herein. This opinion
is made as of the date hereof,  and after the date hereof,  we undertake no, and



The Board of Directors
Entropin, Inc.
April 30, 1998
Page  2

disclaim  any,  obligation  to advise you of any change in any matters set forth
herein.  This  opinion  is  furnished  to you  solely  in  connection  with  the
transactions  referred to herein,  and may not be relied on by any other person,
firm or entity without our prior written consent.

         We  acknowledge  that we are  referred  to  under  the  caption  "Legal
Matters" included in the Registration  Statement.  We hereby consent to such use
of our name in the  Registration  Statement and to the filing of this opinion as
an Exhibit thereto. In giving this consent, we do not thereby admit that we come
within the category of persons whose consent is required  under Section 7 of the
United  States  Securities  Act of  1933 or the  Rules  and  Regulations  of the
Securities and Exchange Commission promulgated thereunder.

                                         Very truly yours,

                                         /S/ Brenman Bromberg & Tenenbaum, P.C.