Exhibit 10.13



                         RELEASE AND AMENDMENT AGREEMENT

     This Release and Amendment Agreement (the "Agreement") is made this 1st day
of May  1998,  by and  between  Pharmaceutical  Resources,  Inc.,  a New  Jersey
corporation ("PRI"), Par Pharmaceutical, Inc., a New Jersey corporation ("Par"),
SANO Corporation, a Florida corporation ("SANO"), and Elan Corporation,  plc, an
Irish company of Lincoln House,  Lincoln Place, Dublin 2, Ireland (together with
its affiliates,  "ELAN").  All  capitalized  terms used herein and not otherwise
defined  herein  shall  have  the  meanings   ascribed  to  them  in  the  Prior
Distribution Agreement (as defined below).

                              W I T N E S S E T H:


     WHEREAS,  SANO,  PRI  and Par  are  parties  to the  Amended  and  Restated
Distribution  Agreement,  dated as of July 28,  1997  (the  "Prior  Distribution
Agreement");

     WHEREAS,  pursuant to the Prior  Distribution  Agreement,  PRI and Par have
exclusive   rights  to  distribute,   among  other  products,   the  transdermal
nitroglycerin  product (general  equivalent of Transderm  Nitro(R)) described as
Product C therein ("Product C"); and

     WHEREAS,  PRI and Par have  agreed  to  release  all of their  rights  with
respect to Product C to ELAN in consideration of the mutual agreements set forth
herein.

     NOW,  THEREFORE,  in  consideration  of the  premises  and  of  the  mutual
agreements set forth herein, the parties hereto agree as follows:

1.       Product  C  Release.   Subject  to  the  terms  and  conditions  hereof
         (including Sections 3 and 5(a) hereof),  PRI and Par hereby release and
         transfer  to ELAN all of their  rights  under  the  Prior  Distribution
         Agreement with respect to Product C (the "Product C Release").  Subject
         to Section 5(a) below,  SANO and ELAN hereby  acknowledge  that PRI and
         Par have no further  obligations or liabilities with respect to Product
         C.

2.       Product A Release.  Subject to Section  5(a)  hereof and Par's right of
         election set forth in Section 6 hereof,  PRI and Par hereby release and
         transfer  to ELAN all of their  rights  under  the  Prior  Distribution
         Agreement  with  respect  to  the  transdermal   nitroglycerin  product
         (generic  equivalent  of Nitro  Dur(R))  described as Product A therein
         ("Product  A").  Subject to Section  5(a)  below,  SANO and ELAN hereby
         acknowledge that PRI and Par have no further obligations or liabilities
         with respect to Product A.






         CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH THE
                       SECURITIES AND EXCHANGE COMMISSION
                         ASTERISKS DENOTE SUCH OMISSION


3.       Consideration.

         (a) The  aggregate  cash  consideration  for the Product C Release (the
         "Consideration") shall be the aggregate of (i) [****] in cash, (ii) the
         royalty payments  described in Section 4 below, (iii) all amounts owing
         under  the  promissory   note  attached  as  Exhibit  C  to  the  Prior
         Distribution  Agreement in the  principal  amount of  $1,953,393  (plus
         accrued  interest of $118,729 from July 28, 1997 to April 15, 1998 plus
         $454.90 per day until  payment of the  amounts due  pursuant to Section
         3(c)  hereof  is made),  plus (iv) all  amounts  owing  under  Sections
         13.14(a) and (c) of the Prior Distribution  Agreement (i.e., [****] and
         [****], respectively).

         (b) The Consideration specified in Section 3(a)(i) and (iv) above shall
         be payable by ELAN to Par in readily  available  funds in the form of a
         certified  check or wire transfer and shall be due and payable no later
         than five days from the date hereof.

         (c) The  Consideration  specified in Section  3(a)(iii)  above shall be
         payable  by SANO to Par in  readily  available  funds  in the form of a
         certified  check or wire transfer and shall be due and payable no later
         than five days from the date  hereof.  Upon  payment  of the  foregoing
         amount, Par shall return to SANO the original  promissory note referred
         to in Section 3(a)(iii) above, marked to reflect its cancellation.

4.       Royalty Payments. (a) ELAN shall pay Par royalty payments (the "Royalty
         Payments")  equal to [****] of all Net Sales of Product C following the
         date  hereof  by ELAN  and its  Affiliates  (and any  transferee(s)  or
         successor(s) of the rights to Product C) and/or, where applicable,  any
         distributors  and  licensees  thereof  (the  "Royalty  Parties") in the
         United  States (as  defined in the Prior  Distribution  Agreement)  and
         Israel.  Par  acknowledges  that it is not entitled to Royalty Payments
         from both ELAN and a  distributor  or  licensee  thereof  in respect of
         sales of the same units of Product C.

         (b)  As used herein,  the term "Net Sales" shall mean the gross amount
         invoiced  for  sales  of  Product  C made by  ELAN or any of the  other
         Royalty Parties to any  unaffiliated  wholesaler,  chain,  distributor,
         repackager, or buying or similar group for eventual sale reduced by the

                                       2


         following  to the  extent  that  they  are  properly  allocable  to the
         quantity of Product C so sold:  all trade,  quantity and cash discounts
         allowed;   credits  or  allowances   actually  granted  on  account  of
         rejections;  returns,  billing errors and retroactive  price reductions
         (including,  without  limitation,  shelf stock  adjustments);  credits,
         rebates,  chargeback rebates, fees,  reimbursements or similar payments
         granted or given to wholesalers and other distributors,  buying groups,
         health  care  insurance  carriers,   governmental  agencies  and  other
         institutions in respect of the purchase price; freight, transportation,
         insurance  or other  delivery  charges;  and all taxes  (except  income
         taxes),  tariffs, duties and other similar governmental charges paid by
         the seller on sales of Product C and not reimbursed by the purchaser.

         (c)   Par's  rights  to the  Royalty  Payments  shall be  irrevocable,
         perpetual,  unconditional  and,  subject to the last  sentence  of this
         subsection (c), not subject to offset for any reason.  Royalty Payments
         shall be payable  quarterly on the 60th day  following  the end of each
         calendar  quarter.  ELAN reserves the right to deduct before  effecting
         payment  to Par the amount of any  taxation  it is  required  by law to
         withhold  from Par in respect of the payment of royalties due hereunder
         to Par.  In the event of any such  deduction,  ELAN  shall  secure  and
         furnish promptly to Par official tax receipts evidencing the payment of
         such taxation.

         (d)  ELAN shall  deliver to Par  quarterly,  on the 60th day following
         the end of each calendar quarter,  a sales summary showing all sales of
         Product C made by ELAN and/or,  where applicable,  by the other Royalty
         Parties during the immediately  preceding calendar quarter, a statement
         certifying its  calculation of the Net Sales from gross revenues during
         such calendar  quarter,  the units of Product C sold, and a computation
         of the amounts due to Par.

         (e)   Subject  to any  contractual  obligation  of ELAN  to the  other
         Royalty  Parties,  ELAN shall make  available for  inspection by Par at
         ELAN's  facilities  such  additional  information  concerning any sales
         and/or any other information provided pursuant to Section 4(d) above as
         Par may  reasonably  request from time to time to enable Par to confirm
         or  reconcile  the  amounts  which  are or were to have been paid to it
         pursuant  to this  Agreement  (without  the need to audit the books and
         records of ELAN pursuant to Section 4(f) hereof).

         (f)   ELAN shall  keep  complete  and  accurate  records  and books of
         account  containing all  information  required for the  computation and
         verification  of  the  amounts  to be  paid  to  Par.  Subject  to  any
         contractual  obligations  of ELAN to the other  Royalty  Parties,  ELAN
         further  agrees  that at the request of Par, it will permit one or more
         accountants  selected  by  Par,  except  any  to  whom  ELAN  has  some
         reasonable objection, at any time and from time to time, to have access
         during  ordinary  working  hours to such records as may be necessary to
         audit,  with respect to any payment  report period ending prior to such
 
                                      3


         request,  the  correctness  of any  report or  payment  made under this
         Agreement, or to obtain information as to the payments due for any such
         period  in the  case  of  failure  of ELAN to  report  or make  payment
         pursuant  to the terms of this  Agreement.  Such  accountant  shall not
         disclose to Par any information relating to the business of ELAN except
         that which is reasonably necessary to inform Par of:

              (i) the accuracy or inaccuracy of ELAN's reports and payments;

              (ii)  compliance  or  non-compliance  by ELAN  with the  terms and
         conditions of this Agreement; and

              (iii)  the  extent  of  any  such  inaccuracy  or  non-compliance;
         provided, that if it is not reasonably possible to separate information
         relating  to the  business  of  ELAN  from  that  which  is  reasonably
         necessary to so inform Par, the accountant may disclose any information
         necessary to so inform Par and Par shall  retain all other  information
         disclosed as confidential.

                  ELAN shall provide full and complete  access to the accountant
         to ELAN's pertinent books and records and the accountant shall have the
         right to make and retain  copies  (including  photocopies).  Should any
         such accountant discover  information  indicating  inaccuracy in any of
         ELAN's  payments  or  non-compliance  by ELAN and  should  ELAN fail to
         acknowledge  in  writing  to  Par  the  deficiency  or   non-compliance
         discovered  by such  accountant  within ten (10) business days of being
         advised of same in writing by the accountant, the accountant shall have
         the right to  deliver  to Par  copies  (including  photocopies)  of any
         pertinent  portions of the records and books of account which relate to
         or  disclose  the  deficiency  or  non-compliance  (to the  extent  not
         acknowledged  by ELAN).  In the event  that the  accountant  shall have
         questions  which  are not in its  judgment  answered  by the  books and
         records  provided to it, the accountant  shall have the right to confer
         with officers of ELAN, including ELAN's Chief Financial Officer. If any
         audit under this Section shall reveal an underpayment or understatement
         of the amount  payable to Par by more than  $5,000.00 for any period in
         question,  ELAN shall reimburse Par for all costs and expenses relating
         to such  investigational  audit. Par shall only have the right to audit
         such books and records of ELAN  pursuant to this  Section  4(f) no more
         often than twice in any contract  year unless  earlier in such contract
         year or in any of the prior  three  contract  years such  investigation
         revealed a discrepancy of more than $5,000.00,  as aforesaid,  in which
         case Par shall  have the right to audit such  books and  records  three
         times in such contract year. For purposes of this Agreement, a contract
         year shall be a period of twelve  months  commencing on either the date
         of this Agreement or on an anniversary  thereof.  Unless the disclosure
         of same is reasonably required by Par in connection with any litigation
         or  arbitration  arising out of such audit,  the  accountant  shall not
         reveal  to Par the name or  address  (or other  information  reasonably
         tending to identify  the  location of a  customer)  of any  customer of
         ELAN,  but shall  identify such  customer to Par, if necessary,  by the
         customer code number used by ELAN in its reporting  obligations  to Par
         and ELAN shall make such information known to the accountant. ELAN may,
         as a condition  to  providing  any  accountant  access to its books and
         records, require Par to execute a reasonable  confidentiality agreement
         consistent  with the  terms  of this  Section  4(f).  
 
                                      4


         (g)  Except as specifically set forth to the contrary, all payments to
         be made under this  Agreement  shall  bear  interest  equal to two (2%)
         percent above the prime rate as quoted by Citibank  N.A., New York, New
         York,  calculated  daily (as at the close of business on each such day)
         and compounded  monthly,  from the day following the day the payment is
         due until  the date on which it is paid.  Any  adjustment  to the prime
         rate as quoted by  Citibank  N.A.  from time to time shall  result in a
         corresponding adjustment to the rate of interest payable hereunder, the
         rate of interest  quoted by  Citibank  N.A. at the close of business on
         each day to be the rate applicable for such day.

         (h)  ELAN shall have sole  discretion  in setting  the sales price for
         the sale of  Product  C,  provided  that ELAN  shall  not  specifically
         discount  the  price of  Product  C for the  benefit  of  ELAN's  other
         products or to otherwise use Product C as a loss leader or incentive to
         procure the sale of ELAN's other  products.  Rebate and other  discount
         programs  (excluding  any  program  where  the  price of  Product  C is
         discounted  primarily  for the benefit of enhancing  the sale of ELAN's
         other products) generally available to ELAN's customers on the purchase
         of  pharmaceutical  products  shall not be  prohibited  by this Section
         4(h),  provided that such programs shall be in accordance with industry
         standards for comparable  products and shall be designed to promote the
         sale of Product C and no other products.

         (i)  ELAN shall use its reasonable  efforts to cause the other Royalty
         Parties to comply with the  provisions  of this  Section 4,  including,
         without  limitation,  to provide  such  information  as is necessary to
         confirm that all  necessary  royalty  payments  shall have been made to
         Par.

5.       Amendment to the Prior Distribution Agreement.

         (a) The Prior  Distribution  Agreement shall be amended and restated as
         set forth in the Amended and Restated Distribution  Agreement,  of even
         date herewith,  by and among SANO, PRI and Par, in the form attached as
         Exhibit A hereto (the "Amended  Distribution  Agreement").  The Amended
         Distribution   Agreement   shall   replace  and   supersede  the  Prior
         Distribution  Agreement in its entirety;  provided,  however,  that any
         agreements  relating to or in  connection  with  Product C or Product A
         which,  pursuant  to the  terms of the  Prior  Distribution  Agreement,
         survive  termination  of the Prior  Distribution  Agreement,  including
         indemnification  obligations,  shall remain in effect on the same terms
         and conditions as provided therein.


                                       5


         (b)   Notwithstanding  any  references  in  the  Amended  Distribution
         Agreement  to Product A, the term  "Licensed  Product"  in the  Amended
         Distribution  Agreement  shall not include Product A and the provisions
         thereof  shall not apply to Product A,  unless and until PRI  exercises
         its right of election set forth in Section 6 below.


         CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH THE
                       SECURITIES AND EXCHANGE COMMISSION
                         ASTERISKS DENOTE SUCH OMISSION


6.       Right of Election.  In the event that ELAN obtains ANDA approval by the
         FDA covering  Product A, PRI shall have the right to elect,  by written
         notice to ELAN and the payment to ELAN of [****],  to include Product A
         as a "Licensed  Product".  In the event that PRI,  makes such election,
         the provisions of the Amended Distribution Agreement will be reinstated
         with respect to Product A on the terms and conditions  provided therein
         as of the date hereof.

7.       Notices.  Any  notice  required  or  permitted  to be given  under this
         Agreement  shall be  sufficiently  given if in writing and delivered by
         registered  or certified  mail (return  receipt  requested),  facsimile
         (with   confirmation   of   transmittal),   overnight   courier   (with
         confirmation of delivery), or hand delivery to the appropriate party at
         the address set forth below, or to such other address as such party may
         from time to time specify for that purpose in a notice similarly given:

                If to SANO:

                       SANO Corporation
                       3250 Commerce Parkway
                       Miramar, Florida 33025
                       Attn: President
                       Fax: (954) 430-3390

                with a copy to (other than regularly prepared notices, reports, 
                etc. required to be delivered hereunder):

                       Greenberg, Traurig, Hoffman,
                       Lipoff, Rosen & Quentel, P.A.
                       1221 Brickell Avenue
                       Miami, Florida 33131
                       Attn: Gary Epstein, Esq.
                       Fax: 305-579-0717

                If to ELAN:

                       Elan Corporation, plc
                       Lincoln House
                       Lincoln Place
                       Dublin 2, Ireland
                       Attn: Vice President and General Counsel
                       Elan Pharmaceutical Technologies, a division of
                       Elan Corporation, plc
                       Fax: (011) 353-1-662-4960

                                       6


                If to PRI or Par:

                       c/o PRI Distributors, Ltd.
                       One Ram Ridge Road
                       Spring Valley, NY 10977
                       Attn: President
                       Fax: 914-425-7922

                with a copy to (other than regularly prepared notices, reports,
                etc. required to be delivered hereunder):

                       Hertzog, Calamari & Gleason
                       100 Park Avenue
                       New York, New York 10017
                       Attn:  Stephen A. Ollendorff, Esq. and
                       Stephen R. Connoni, Esq.
                       Fax:  (212) 213-1199

         Any such notice shall be effective  (i) if sent by mail (or in the case
         of notice to or by ELAN by  registered  airmail),  as  aforesaid,  five
         business days after mailing,  (ii) if sent by facsimile,  as aforesaid,
         when  sent,  and  (iii)  if  sent by  courier  or  hand  delivered,  as
         aforesaid,  when received.  Provided that if any such notice shall have
         been sent by mail and if on the date of  mailing  thereof or during the
         period prior to the expiry of the third business day following the date
         of mailing  there shall be a general  postal  disruption  (whether as a
         result of rotating strikes or otherwise) in the United States then such
         notice  shall  not  become  effective  until  the  fifth  business  day
         following the date of resumption of normal mail service.


                                       7



8.       Governing Law and Consent to Jurisdiction.

         (a) Except as otherwise provided herein, this Agreement shall be deemed
         to have been made  under,  and shall be  governed  by,  the laws of the
         State of Florida in all  respects  including  matters of  construction,
         validity and performance, but without giving effect to Florida's choice
         of law provisions.

         (b) In  connection  with any action  commenced  hereunder,  each of the
         undersigned  consent  to the  exclusive  jurisdiction  of the state and
         federal  courts  located  in  Miami,   Florida.   Notwithstanding   the
         foregoing,  each party  also  agrees to the  jurisdiction  of any court
         which a third party claim has been brought.

9.       Binding  Agreement.  This  Agreement  shall be binding upon the parties
         hereto, and their respective successors and permitted assigns.

10.      Counterparts.  This  Agreement  may be executed in identical  duplicate
         copies.  The parties agree to execute at least two  identical  original
         copies of the Agreement.  Each identical counterpart shall be deemed an
         original,  but all of which together shall  constitute one and the same
         instrument.

11.      Severability of Provisions.  If, for any reason  whatsoever,  any term,
         covenant or  condition of this  Agreement  or of any other  document or
         instrument executed and delivered by either Par or ELAN pursuant hereto
         or in connection  with the completion of the  transaction  contemplated
         herein,  or the application  thereof to any party or circumstance is to
         any extent held or rendered  invalid,  unenforceable  or illegal,  then
         such term, covenant or condition:

                  (i) is  deemed  to be  independent  of the  remainder  of such
                  document and to be severable and  divisible  therefrom and its
                  validity,  unenforceability  or  illegality  does not  affect,
                  impair or  invalidate  the  remainder of such  document or any
                  part thereof; and

                  (ii) continue to be applicable and  enforceable to the fullest
                  extent  permitted  by law against any party and  circumstances
                  other  than  those as to which  it has been  held or  rendered
                  invalid, unenforceable or illegal.

12.      Entire   Agreement.   This   Agreement,   together   with  the  Amended
         Distribution Agreement,  represents the entire agreement of the parties
         with  respect  to the  subject  matter  hereof,  superseding  all prior
         agreements and understandings, written or oral.

                                       8


                  IN WITNESS WHEREOF,  this Release and Amendment  Agreement has
been  executed and  delivered  by the parties  hereto as of the date first above
written.

                            PHARMACEUTICAL RESOURCES, INC.
 


                           By: /s/Kenneth I. Sawyer
                              --------------------------------------
                              Name: Kenneth I. Sawyer
                              Title:   President and Chief Executive Officer

                           PAR PHARMACEUTICAL, INC.


                           By: /s/Kenneth I. Sawyer
                               --------------------------------------
                               Name: Kenneth I. Sawyer
                               Title: President and Chief Executive Officer

                           SANO CORPORATION


                           By: /s/Reginald Hardy
                              --------------------------------------
                              Name: Reginald Hardy
                              Title:   President

                           ELAN CORPORATION, PLC


                           By: /s/Thomas G. Lynch
                              --------------------------------------
                              Name: Thomas G. Lynch
                              Title:   Executive Vice President and
                                       Chief Financial Officer



                                       9