[L&W LETTERHEAD]


                                                   March 10, 1999


Algos Pharmaceutical Corporation
1333 Campus Parkway
Neptune, New Jersey

      Re: Registration Statement No. 333-______ on Form S-3; with respect
          to 3,200,000 shares of Common Stock, par value $.01 per share

Ladies and Gentlemen:

          In connection with the registration of 3,200,000 shares of common
stock of Algos Pharmaceutical Corporation, a Delaware corporation (the
"Company"), par value $.01 per share (the "Shares"), under the Securities Act
of 1933, as amended (the "Act"), by the Company on Form S-3 filed with the
Securities and Exchange Commission (the "Commission") on March 10, 1999
(File No. 333-____), you have requested our opinion with respect to the
matters set forth below.

          In our capacity as your counsel in connection with such registration,
we are familiar with the proceedings taken and proposed to be taken by the
Company in connection with the authorization, issuance and sale of the Shares,
and for the purposes of this opinion, have assumed such proceedings will be
timely completed in the manner presently proposed. In addition, we have made
such legal and factual examinations and inquiries, including an examination
of originals or copies certified or otherwise identified to our satisfaction
of such documents, corporate records and instruments, as we have deemed
necessary or appropriate for purposes of this opinion.

          In our examination, we have assumed the genuineness of all signatures,
the authenticity of all documents submitted to us as originals, and the
conformity to authentic original documents of all documents submitted to us as
copies.

          We are opining herein as to the effect on the subject transaction only
of the internal laws of the State of New York and the General Corporation Law of
the State of Delaware, and we express no opinion with respect to the
applicability thereto, or the effect thereon, of the laws of any other
jurisdiction or, in the case of Delaware, any other laws, or as to matters of
municipal law or the laws of any local agency within any state.

          Subject to the foregoing, it is our opinion that those Shares that
have been issued and are outstanding as of the date hereof have been duly
authorized and were, at issuance, validly issued, fully paid and nonassessable.

          Subject to the foregoing, it is our opinion that those Shares
that have not been issued as of the date hereof but are subject to issuance
pursuant to the terms and conditions of a warrant, will, upon issuance,
delivery and payment therefor, be validly issued, fully paid and nonassessable.





Algos Pharmaceutical Corporation
March 10, 1999
Page 2


          It is our understanding that this opinion is to be used only in
connection with the offer and sale of the Shares while the Registration
Statement is in effect.

          We consent to your filing this opinion as an exhibit to the
Registration Statement and to the reference to our firm contained under the
heading "Legal Matters."

                                                   Very truly yours,

                                                   /s/ Latham & Watkins