Document:

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                                                                   EXHIBIT 10.20

$ 30,000,000.00                                           New York, New York
                                                          December 19, 2002

1. OBLIGATION TO PAY

         FOR VALUE RECEIVED, the undersigned Borrower promises to pay to the
order of MICHAEL JAHARIS, an individual residing in New York, New York (the
"Lender"), the principal sum of Thirty Million Dollars ($30,000,000.00), on June
30, 2008, or such amount thereof as shall be outstanding hereunder on such date,
plus interest payable at the rate and in the manner provided in paragraph 3 of
this Additional Standby Facility Note, plus any costs and expenses incurred in
the enforcement of this Additional Standby Facility Note as provided in
paragraph 7 of this Additional Standby Facility Note. This Additional Standby
Facility Note is transferable by the holder hereof.

This Additional Standby Facility Note is issued pursuant to the Additional
Standby Facility Loan Agreement (as hereinafter defined), reference to which is
hereby made for other terms applicable to this Additional Standby Facility Note.

2. DEFINITIONS

         Except as otherwise defined herein, all capitalized terms used herein
which are defined in the Additional Standby Facility Loan Agreement shall have
the meaning ascribed to them therein. In addition, the following terms as used
herein shall be defined as follows:

                  (A) "Common Stock" shall mean the capital common stock of the
Borrower, consisting of 50,000,000 authorized shares $.01 par value.

                  (B) "Event of Default" shall mean any of the events set forth
in Paragraph 7 hereof.

                  (C) "First Advance Date" shall mean the date of the first
advance under this Additional Standby Facility Note and the Additional Standby
Facility Loan Agreement.

                  (D) "Interest Adjustment Date" shall mean the first day of
each month during the term of this Additional Standby Facility Note.

                  (E) "Additional Standby Facility Loan Agreement" shall mean a
Revolving Credit and Loan Agreement of even date herewith between Borrower and
the Lender pursuant to which this Additional Standby Facility Note is issued, as
the same may be amended and supplemented from time to time.

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                  (F) "Additional Standby Facility Loan Documents" shall mean
this Additional Standby Facility Note, the Additional Standby Facility Loan
Agreement, the Third Amended and Restated Registration Rights Agreement, the
Second Amended and Restated Security Agreement, the Second Amended and Restated
Patent Security Agreement, the Second Amended and Restated Stock Pledge
Agreement, the ATI Second Amended and Restated Subsidiary Guaranty, the ATI
Second Amended and Restated Subsidiary Security Agreement, the ATI Amended and
Restated Subsidiary Stock Pledge Agreement, the IEP Amended and Restated
Subsidiary Guaranty, the IEP Amended and Restated Subsidiary Security Agreement,
the UCC-1 financing statements executed in connection with the security
agreements, the Warrant, and each and every other document executed or delivered
in connection with the closing of this transaction, each such document being
referred to individually as a "Additional Standby Facility Loan Documents".

                  (G) "Prime Rate" shall mean the prime rate (or substantially
equivalent index, if such bank discontinues its prime rate) of SunTrust Bank
Miami, N.A., as announced from time to time, or, if such bank shall cease to
exist without any successor-in-interest, then the prime rate (or substantially
equivalent index, if no prime rate exists at such bank at such time) of any
national or regional bank selected by Lender having a comparable or larger asset
size.

                  (H) "Warrant" shall mean that certain Non-Detachable Common
Stock Purchase Warrant to purchase one million shares of Common Stock, as more
particularly described in the Additional Standby Facility Loan Agreement.

3. INTEREST

         The outstanding principal balance of this Additional Standby Facility
Note shall bear interest from the date hereof until the earlier of maturity,
imposition of the Default Rate (as hereinafter defined) or payment in full, at a
rate per annum equal to the Prime Rate in effect on each Interest Adjustment
Date (calculated on the basis of a 360-day year for the actual number of days
elapsed), on which date the interest rate shall be increased or decreased to the
extent of any increase or decrease in the Prime Rate from the Prime Rate in
effect on the immediately preceding Interest Adjustment Date. After maturity, or
upon the occurrence of and during the continuance of an Event of Default, if
earlier, the interest rate hereunder shall be increased to a rate equal to six
(6.0) percentage points in excess of the rate which would otherwise be in effect
hereunder.

         Notwithstanding any provision of this Additional Standby Facility Note
to the contrary, in the event that at any time the applicable rate of interest
payable by Borrower to Lender as stated in this Additional Standby Facility Note
(the "Contract Rate") exceeds the highest or maximum rate of interest
permissible to be charged by Lender under the laws of the State of New York or
under federal law, or is determined by a tribunal or court of competent
jurisdiction to be excessive and unenforceable (in each case, the "Maximum Legal
Rate"), then the interest rate payable under this Additional Standby Facility

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Note shall automatically be reduced to the Maximum Legal Rate for such period as
the Maximum Legal Rate is higher than the Contract Rate. If subsequently the
Contract Rate becomes less than the Maximum Legal Rate, then the interest rate
payable under this Additional Standby Facility Note shall automatically be
decreased to the Contract Rate. Any amounts paid in excess of the Maximum Legal
Rate shall be considered to have been payments in reduction of principal, and
the outstanding principal balance shall be adjusted to reflect such prepayments
of principal.

4. PAYMENTS

         Accrued interest shall be due and payable monthly on the seventh day of
each month. Interest may, at the option of the holder hereof, be deducted from
the amount of the proceeds of any disbursements hereunder.

         Upon maturity, the outstanding principal balance of this Additional
Standby Facility Note, together with unpaid interest accrued thereon and any
other sums payable hereunder, shall be payable in full.

         All sums received hereunder shall be applied first to the payment of
late charges, costs and expenses payable to Lender hereunder, then to interest
(in the order in which earliest earned) and the balance to principal. Borrower
shall have the right to prepay this Additional Standby Facility Note in full or
in part at any time without penalty.

         All payments shall be made in accordance with the terms of the
Additional Standby Facility Loan Agreement and shall be delivered to Lender at
its address at Michael Jaharis, c/o Steven K. Aronoff, P.C., 475 Park Avenue
South, 23rd Floor, New York, New York 10016 or at such other address as shall be
designated by Lender in a written notice to the Borrower.

         This Additional Standby Facility Note may also be prepaid in part or in
full by the holder of this Additional Standby Facility Note exercising the
Warrant in accordance with the terms of the Warrant. No partial prepayment of
this Additional Standby Facility Note by exercise of the Warrant shall abate
Borrower's obligation to make monthly interest payments on the reduced principle
balance, nor shall any such partial prepayment extend the maturity date of this
Additional Standby Facility Note.

5. ADVANCES

         Advances shall be made hereunder from time to time in accordance with
the terms of the Additional Standby Facility Loan Agreement, reference to which
is hereby made for the provisions regarding advances. At no time shall the
aggregate of all advances outstanding from time to time exceed $30,000,000.00.

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6. LATE CHARGE

         If any monthly payment of interest is not received by the Lender or any
holder hereof within 15 days after its due date, there shall be imposed on the
Borrower a late charge equal to five (5.0%) percent of such overdue payment.

7. ENFORCEMENT

         Upon the occurrence of an Event of Default (as hereinafter defined),
the entire principal balance remaining unpaid plus accrued interest shall, at
the option of the holder hereof, become immediately due and payable, and the
Borrower shall have all of the rights and remedies provided in the Additional
Standby Facility Loan Agreement and shall be entitled to be reimbursed for its
costs and expenses as set forth therein.

         An Event of Default is defined as any one of the following: (i) default
in the payment of any principal, interest or other amounts within ten (10) days
after such payment is due hereunder; (ii) breach of any provisions of this
Additional Standby Facility Note; or (iii) the occurrence of any Event of
Default under the Additional Standby Facility Loan Agreement.

         No extension of time for payment, or delay in enforcement hereof, nor
any renewal of this Additional Standby Facility Note with or without notice,
shall release the obligation of the Borrower to the Lender or holder hereof or
shall operate as a waiver of any of its rights.

         Presentment, demand, protest and notice of dishonor are hereby waived
by the Borrower.

8. RIGHT OF SETOFF

         Upon the occurrence of and during the continuance of any Event of
Default hereunder, the Lender is hereby authorized at any time and from time to
time, without notice to the Borrower (any such notice being expressly waived by
the Borrower) to set-off and apply any and all indebtedness at any time owing by
the Lender to or for the credit or the account of the Borrower against any and
all of the obligations of the Borrower now or hereafter existing under this
Additional Standby Facility Note or the Additional Standby Facility Loan
Agreement, irrespective of whether or not the Lender shall have made any demand
under this Additional Standby Facility Note or the Additional Standby Facility
Loan Agreement. The Lender agrees promptly to notify the Borrower after any such
setoff and application made by the Lender, provided that the failure to give
such notice shall not affect the validity of such setoff and application. The
rights of the Lender under this provision are in addition to other rights and
remedies (including, without limitation, any common law right of setoff) which
the Lender may have.

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9. WAIVER OF RIGHTS

         BORROWER ACKNOWLEDGES THAT THE TRANSACTION OF WHICH THIS ADDITIONAL
STANDBY FACILITY NOTE IS A PART IS A COMMERCIAL TRANSACTION. BORROWER HEREBY
WAIVES, TO THE EXTENT PERMITTED BY LAW, THE BENEFITS OF ALL VALUATION,
APPRAISEMENT, HOMESTEAD, EXEMPTION, STAY, REDEMPTION AND MORATORIUM LAWS, NOW IN
FORCE OR WHICH MAY HEREAFTER BECOME LAW.

10. SUBMISSION TO JURISDICTION; WAIVER OF BOND

         THE BORROWER HEREBY CONSENTS TO THE JURISDICTION OF ANY LOCAL, STATE,
OR FEDERAL COURT LOCATED WITHIN THE STATE OF NEW YORK AND WAIVES ANY OBJECTION
WHICH BORROWER MAY HAVE, BASED ON IMPROPER VENUE OR FORUM NON CONVENIENS, TO THE
CONDUCT OF ANY PROCEEDING IN ANY SUCH COURT AND WAIVES PERSONAL SERVICE OF ANY
AND ALL PROCESS UPON BORROWER, AND CONSENTS THAT ALL SUCH SERVICE OF PROCESS BE
MADE BY MAIL OR MESSENGER DIRECTED TO BORROWER AT THE ADDRESS SET FORTH BELOW
AND THAT SERVICE SO MADE SHALL BE DEEMED TO BE COMPLETED UPON THE EARLIER OF
ACTUAL RECEIPT OR THREE (3) DAYS AFTER THE SAME SHALL HAVE BEEN POSTED TO
BORROWER'S ADDRESS. THE BORROWER WAIVES ANY BOND OR SURETY OR SECURITY UPON SUCH
BOND WHICH MIGHT, BUT FOR THIS WAIVER, BE REQUIRED OF THE LENDER. NOTHING
CONTAINED IN THIS PARAGRAPH AFFECTS THE RIGHT OF THE LENDER TO SERVE LEGAL
PROCESS IN ANY OTHER MANNER PERMITTED BY LAW OR AFFECTS THE RIGHT OF THE LENDER
TO BRING ANY ACTION OR PROCEEDING AGAINST BORROWER OR BORROWER'S PROPERTY IN THE
COURTS OF ANY OTHER JURISDICTION.

11. WAIVER OF JURY TRIAL

         THE BORROWER WAIVES, TO THE EXTENT PERMITTED BY LAW, ANY RIGHT TO TRIAL
BY JURY WHICH BORROWER MAY HAVE IN ANY PROCEEDING BETWEEN LENDER AND BORROWER.

12. WAIVER OF PLAINTIFF'S RIGHTS

         THE BORROWER HEREBY AGREES NOT TO COMMENCE ANY LEGAL PROCEEDING AGAINST
THE LENDER IN THE JURISDICTION OF ANY LOCAL, STATE, OR FEDERAL COURT LOCATED

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WITHIN THE STATE OF FLORIDA UNLESS THE LENDER EXPRESSLY CONSENTS THERETO IN
WRITING.

13. GOVERNING LAW

         This Additional Standby Facility Note and its interpretation,
construction, validity and enforceability shall be governed by the laws of the
State of New York.

                                             KOS PHARMACEUTICALS, INC.

                                             By:
                                                --------------------------------
                                                 Name:  Adrian Adams
                                                 Title: President

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STATE OF NEW YORK      )
                       )  ss.:
COUNTY OF              )

         On the ______ day of December ___, 2002, before me came Adrian Adams,
to me known, who, being by me duly sworn, did depose and say that he resides at
No.________________ _______________________________________________; that he is
the President of Kos Pharmaceuticals, Inc., the corporation described in and
which executed, the foregoing instrument; that the foregoing instrument was
executed without corporate seal by order of the Board of Directors of said
corporation; that he signed his name thereto by like order.

                                                --------------------------------
                                                Notary Public
                                                My commission expires:

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                                                                   EXHIBIT 10.21

         THIS WARRANT AND THE SECURITIES ISSUABLE UPON EXERCISE HEREOF HAVE NOT
         BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
         SECURITIES LAW. NEITHER THIS WARRANT NOR THE SECURITIES ISSUABLE UPON
         EXERCISE HEREOF NOR ANY INTEREST OR PARTICIPATION HEREIN OR THEREIN MAY
         BE SOLD, ASSIGNED, PLEDGED OR DISPOSED OF EXCEPT IN COMPLIANCE WITH THE
         SECURITIES ACT OF 1933 AND ALL STATE SECURITIES LAWS AND THE TERMS AND
         CONDITIONS HEREOF.

                  NON-DETACHABLE COMMON STOCK PURCHASE WARRANT

                            Void After June 30, 2009

         This is to certify that, for value received, Michael Jaharis, or
registered assigns thereof (the "Holder"), is entitled to purchase from Kos
Pharmaceuticals, Inc., a Florida corporation (the "Corporation"), at the price
per share set forth in paragraph 2 below (the "Warrant Price") at any time on or
before June 30, 2009, all or any part of 1,000,000 shares of Common Stock, par
value $.01 per share, of the Corporation ("Common Stock"), on the terms and
subject to the conditions hereinafter set forth. This Warrant is being issued to
the Holder in connection with a loan to the Corporation by the Holder pursuant
to that certain $30,000,000 Revolving Credit and Loan Agreement dated December
19, 2002 between the Corporation and the Holder (the "Loan Agreement"), as
evidenced by that certain promissory note of even date therewith in such
principal sum from the Corporation in favor of the Holder (the "Note").

         1. This Warrant will become void, and all rights of the Holder will
expire, at 5:00 P.M., Miami, Florida local time, on June 30, 2009.

         2. The Warrant Price shall be determined as the average of the per
share closing bid prices for Common Stock, as reported on the National Market of
the National Association of Securities Dealers, Inc. Automated Quotation System
(NASDAQ), rounded up to the nearest $0.125, for the thirty trading days
immediately preceding the First Advance Date (as such term is defined in the
Note).

         3. This Warrant may be exercised by the Holder, upon surrender of the
Note (if the Note is outstanding), as to all or any portion of the shares of
Common Stock covered hereby, by surrender by the Holder or his agent of this
Warrant to the Corporation at its principal office, with the form of Election to
Purchase attached hereto duly executed. Upon any such exercise, the Warrant
Price for such shares shall be paid and satisfied only through the conversion of
principal or interest outstanding under the Note in an aggregate amount equal to
the Warrant Price for such shares. This Warrant shall be exercisable only for so
long as and to the extent of the aggregate amount of principal and interest
outstanding under the Note. The Election to Purchase shall state the name of the
person or entity exercising the Warrant (with address and such further
information as may be required by the Corporation) and the certificate or
certificates for shares of Common Stock shall be issued in this name. Thereupon
this Warrant shall be deemed to have been exercised and the person or entity

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exercising the Warrant shall be deemed to have become a holder of record of
shares of Common Stock purchased hereunder for all purposes and thereafter the
Holder may exercise all rights and be entitled to all benefits of a shareholder
of record of the Corporation, and a certificate or certificates for such shares
so purchased shall be delivered to the person or entity exercising the Warrant
within a reasonable time after this Warrant shall have been exercised as set
forth hereinabove.

         4. The following adjustments shall be made:

                  a. In the event that, prior to the exercise of this Warrant
and issuance of the underlying shares, there shall be an increase or decrease in
the number of issued shares of Common Stock of the Corporation as a result of a
subdivision or consolidation of shares or other capital adjustment, or the
payment of a stock dividend or other increase or decrease in such shares,
effected without receipt of consideration by the Corporation, the remaining
number of shares shall be adjusted so that the adjusted number of shares subject
to this Warrant and the adjusted Warrant Price shall be the substantial
equivalent of the remaining number of shares still subject to the Warrant and
the Warrant Price thereof prior to such change.

                  b. If at any time while this Warrant is outstanding another
corporation merges into the Corporation, the Holder of this Warrant shall be
entitled, immediately after the merger becomes effective and upon exercise of
this Warrant, to obtain the same number of shares of Common Stock of the
Corporation (or shares into which the Common Stock has been changed as provided
in the paragraph of this Warrant covering changes) that the Holder would have
been entitled upon the exercise hereof to obtain immediately before the merger
became effective at the same Warrant Price. The Corporation shall take any and
all steps necessary in connection with the merger to assure that sufficient
shares of Common Stock to satisfy all conversion and purchase rights represented
by outstanding convertible securities, options and warrants, including this
Warrant, are available so that these convertible securities, options and
warrants, including this Warrant, may be exercised.

                  c. On the happening of an event requiring an alteration or
adjustment of the shares purchasable upon exercise of this Warrant, or an
alteration or adjustment of their number or designation, the Corporation shall
give written notice to the Holder of this Warrant stating the adjusted number,
designation and kind of securities or other property obtainable upon exercise of
this Warrant as a result of and following the event. The notice shall set forth
in reasonable detail the method of calculation determining the securities or
property obtainable after the event, and the facts upon which the calculation is
based. The Corporation's board of directors, acting in good faith, shall
determine the calculation.

         5. This Warrant is exchangeable by the Holder, upon the surrender of
the Warrant at the principal office of the Corporation, for new Warrants of like
tenor and date representing in the aggregate the right to subscribe for and
purchase the number of shares of Common Stock which may be subscribed for and
purchased hereunder.

         6. The Corporation covenants and agrees that all shares of Common Stock
which may be issued upon the exercise of the rights represented by this Warrant
will, upon issuance, be validly issued, fully paid and non-assessable and free
from all taxes, liens and charges with respect to the issue thereof except for
any taxes required in connection with the transfer thereof. The Corporation

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further covenants and agrees that, during the period within which the rights
represented by this Warrant may be exercised, the Corporation will at all times
have authorized and reserved a sufficient number of shares of Common Stock to
provide for the exercise of the rights represented by this Warrant.

         7. The Holder of this Warrant, by acceptance hereof, agrees that,
except as hereinafter stated, such holder will not sell, hypothecate or
otherwise transfer or dispose of this Warrant or the shares of Common Stock
issuable on the exercise hereof without giving prior written notice to the
Corporation of such holder's intention to do so, describing briefly the manner
of any such proposed transfer. Notwithstanding the foregoing, this Warrant is
transferable (i) to a trust in which a Holder or Holders is/are the settlor(s)
and either one or more Holders and/or direct family members of such Holder
is/are a primary beneficiary or beneficiaries, (ii) a corporation, partnership
or limited liability company in which one or more Holders and/or direct family
members of such Holders control at least 80 percent of the stockholder,
partnership or membership interests in such corporation, partnership or limited
liability company; or (iii) by descent upon death to direct family members of
such Holders. This Warrant and the rights evidenced hereby shall be transferable
only when attached to the Note. Upon the request of the Corporation, the Holder
proposing to transfer this Warrant shall be required to deliver to the
Corporation an opinion of counsel for the Holder stating that the proposed
transfer described in the notice given by the Holder may be effected without
registration of this Warrant or the shares of Common Stock issuable on the
exercise hereof under the Securities Act of 1933, as then in effect, or any
similar federal statute (the "Securities Act").

         8. The restrictions in Section 6 hereof shall be binding upon any
transferee who has received this Warrant or shares of Common Stock issuable on
exercise hereof. A legend in substantially the following form shall be typed,
printed or stamped on the face and back of all certificates issued on exercise
of this Warrant and on the face and back of all certificates issued in
substitution or exchange thereof:

                    "This security has not been registered under the Securities
               Act of 1933, as amended. It has been acquired for investment and
               may not be sold or transferred in the absence of an effective
               registration statement with respect thereto under the Securities
               Act of 1933, as amended, or an opinion of counsel acceptable to
               the Company that registration is not required under said Act."

         9. The issue of any stock or other certificate upon the exercise of
this Warrant shall be made without charge to the registered holder hereof for
any tax in respect of the issue of such certificate.

         10. This Warrant and all rights hereunder are transferable on the books
of the Corporation (subject, however, to the provisions of Sections 7 and 8
hereof), upon surrender of this Warrant, with the form of Transfer of Warrant
attached hereto duly executed by the registered holder hereof or by his attorney
duly authorized in writing, to the Corporation at its principal office, and
thereupon there shall be issued in the name of the transferee or transferees, in
exchange for this Warrant, a new Warrant or Warrants of like tenor and date,
representing in the aggregate the right to subscribe for and purchase the number
of shares of Common Stock which may be subscribed for and purchased hereunder.

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         11. The Corporation may deem and treat the registered holder of this
Warrant as the absolute owner of this Warrant for all purposes and shall not be
affected by any notice to the contrary.

         12. This Warrant shall not entitle the Holder to any rights of a
stockholder of the Corporation, either at law or in equity, including, without
limitation, the right to vote, to receive dividends and other distributions, to
exercise any preemptive rights or to receive any notice of meetings of
stockholders or of any other proceedings of the Corporation.

         13. This Warrant shall be governed by the laws of the State of Florida.

Dated: December 19, 2002                      KOS PHARMACEUTICALS, INC.

                                              By:
                                                 -------------------------------
                                                  Adrian Adams, President

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