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                                                                  EXHIBIT 10.28

[DAS LOGO]

DRUGABUSE SCIENCES, INC.
1430 O'Brien Drive, Suite E
Menlo Park, CA 94025
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                                         (650) 462-1000     FAX: (650) 462-1003

December 29, 1999

Jason A. Gross, Pharm. D.                  Re:  Employment Agreement
P. O. Box 229
Norwood, NJ  07648

Dear Jason:

On behalf of DrugAbuse Sciences, I am pleased to confirm our proposal for you
to become a DrugAbuse Sciences employee. This offer is conditional upon our
completion of satisfactory referencing, your acceptance of the terms and
conditions of this offer of employment and your execution of the attached
Employee Confidential Information and Inventions Agreement.

Your position with DrugAbuse Sciences, Inc. will be Vice President,
Regulatory Affairs and Quality Assurance, reporting to the CEO. As we
discussed, your position is a full-time position and your employment will
commence no later than January 17, 2000 (the date your employment commences
is referred to as your Start Date.)

Your total full time base salary will be $152,000 per year, payable at the
frequency and in accordance with DrugAbuse Sciences' regularly established
payroll policies. All payments to you will be subject to legally required
withholding. It is DrugAbuse Sciences' policy to review salary and
compensation levels periodically. Accordingly, your base salary and other
compensation may be adjusted from time to time at DrugAbuse Sciences' sole
discretion; raises in compensation are not guaranteed. In addition to your
base salary, you may receive within three months following each yearend, at
the Board of Directors sole discretion, up to a 20% bonus (i.e. 20% of the
paid base salary) subject to meeting specific annual milestones defined by
DrugAbuse Sciences CEO (Attachment A).

DrugAbuse Sciences also has a company Stock Option Plan (which the company
may modify from time to time) that may permit our employees to participate in
the equity ownership of the company. We expect to include you as a
participant in that plan and will recommend to the Company's Board of
Directors that you be granted a stock option for a

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total of 400,000 shares of common stock (based on the October 1999
capitalization table, at a price not to exceed 10 cents per share). These
options will be subject to the terms of the then applicable Stock Option
Plan, and to the following vesting schedule: (i) 5,000 shares would vest
monthly over four years (up to 240,000 shares); (iii) 160,000 shares would
vest solely upon the sixth anniversary of continuous employment, subject to
potential partial acceleration at the sole discretion of the board of
directors, and subject to fully and timely achieving the following milestones:

     (1)  For 30,000 shares: Upon Naltrel NDA FDA filing (50% for the opiate
          indication and 50% for the alcohol indication) if by March 30, 2001

     (2)  For 40,000 shares: Upon Naltrel NDA FDA approval (50% for the opiate
          indication and 50% for the alcohol indication) and commercial launch,
          if by December 31, 2001

     (3)  For 30,000 shares: Upon Naltrel NDA European approval (50% for the
          opiate indication and 50% for the alcohol indication) and commercial
          launch, if by June 30, 2002 for the first country and December 31,
          2002 for 5 EU countries, including France, Germany, UK

     (4)  For 40,000 shares: Upon FDA NDA approval for a second new therapeutic
          product developed by DAS (Buprel or COC-AB) and commercial launch, if
          by December 31, 2002

     (5)  For 20,000 shares: Upon European NDA approval (including UK, Germany
          and France) for a second new therapeutic product developed by DAS
          (Buprel or COC-AB) and commercial launch, if by December 31, 2002.

You will also be eligible to participate in the employee benefits
collectively available to our employees, including medical, dental and
disability coverage. As a regular employee of the Company, you will accrue
annually a total of twelve days vacation and be entitled to the standard
Company holidays.

You will devote your best efforts to the performance of your work for
DrugAbuse Sciences. While employed at DrugAbuse Sciences, you will not
undertake any other activity requiring your business time and attention, nor
will you support any activity that is competitive with DrugAbuse Sciences'
business or pose a conflict of interest with that business. You will follow
all DrugAbuse Sciences' policies and procedures as made available to you from
time to time. As a condition of your employment, you will execute DrugAbuse
Sciences' Employee Confidential Information and Inventions Agreement.

You will exercise best efforts to relocate to the Bay Area within three
months from Start Date. Upon your relocation, the company will pay for direct
moving expenses (excluding realtor fees) up to $22,000 (Should you resign
within 12 months of relocation, you would immediately reimburse $22,000 to
the company).

Your employment with DrugAbuse Sciences will be "at will"; in other words,
either you or DrugAbuse Sciences will have the right to terminate your
employment with DrugAbuse Sciences at any time, for any reason, with or
without notice and with or without cause, in your or our sole discretion. A
total of four months Start Date base salary would be paid to you if the
agreement was terminated by the company without cause.

Jason, we are very excited about your joining us. Please sign and return a
copy of this letter and the attached Employee Confidential Information and
Inventions Agreement to me, keeping a copy of each for your records (this
offer will expire, if not executed, by December

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30, 1999). The terms set forth in this letter supersede all prior agreements,
understandings and representations between us concerning the subject matter
of this letter. Changes to your employment agreement would apply only if in
writing and signed by the DrugAbuse Sciences Inc. CEO. We look forward to you
becoming a member of our team!

Sincerely,

/s/ Philippe Pouletty

Philippe Pouletty, M.D.
Chairman and CEO, DAS Inc.

I, Jason Gross, understand and agree to the above terms. I understand that my
employment with DrugAbuse Sciences is at will, and I acknowledge that no
representations or promises other than those set forth above have been made
to me with regard to the terms and conditions of my employment.

Signed: /s/ Jason Gross                       Date:
        --------------------------------            ------------------------

ATTACHMENT A

First year potential 20% Cash Bonus based on fully and timely achieving three
key milestones over the first twelve months, and at the sole discretion of
the board of directors:

     (1)  Prepare and QA Naltrel NDA filing with all available information

     (2)  Obtain / clear US and EU INDs for Naltrel, COC-Ab (by April 2000) and
          Buprel (by July 2000)

     (3)  Ensure quality assurance / process validation / generation of
          necessary stability studies for Naltrel and COC-Ab<PAGE>
                                                                   Exhibit 10.29
[LOGO]

DRUGABUSE SCIENCES, SA
2 rue de Crucy
44 000 Nantes
France

June 9, 1999

Maryvonne Hiance
35 Rue Edison
44000 Nantes

Re:  Employment Agreement

Dear  Maryvonne:

On behalf of DrugAbuse Sciences, I am pleased and delighted to confirm the terms
of your employment with DrugAbuse Sciences, SAS, located 2 rue de Crucy 44000
Nantes.This offer is conditional upon your acceptance of the terms and
conditions of this offer of employment and your execution of the attached
Employee Confidential Information and Inventions Agreement. Effective June 9,
1999, you will be employed as General Manager, in charge of the European
operations, reporting to the President , DAS SA.

Your base salary will be $60,000 per year, payable at the frequency and in
accordance with DrugAbuse Sciences' regularly established payroll policies. All
payments to you will be subject to legally required withholding. It is DrugAbuse
Sciences' policy to review salary and compensation levels periodically.
Accordingly, your base salary and other compensation may be adjusted from time
to time at DrugAbuse Sciences' sole discretion; raises in compensation are not
guaranteed. In addition you will retain the rights to the options already
granted to you as President (From April 8, 1998), subject to the terms agreed by
the Board, subject to continuous employment.

You will also be eligible to participate in the employee benefits collectively
available to our employees. As a regular employee of the Company, you will
accrue annually a total of five weeks vacation and be entitled to the standard
Company holidays.

You will devote your best efforts to the performance of your job for DrugAbuse
Sciences, SAS. While employed at DrugAbuse Sciences SAS, you will not undertake
any other activity requiring your business time and attention, nor will you
support any activity that is competitive with DrugAbuse Sciences' business or
pose a conflict of interest with that business. You will follow all DrugAbuse
Sciences' policies and procedures (including our policies protecting other
employees against discrimination and sexual harassment) as made available to you
from time to time. As a condition of your employment, you will execute DrugAbuse
Sciences' Employee Confidential Information and Inventions Agreement.

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Page 2 of 2

Please sign and return a copy of this letter and the attached Employee
Confidential Information and Inventions Agreement to me, keeping a copy of each
for your records. The terms set forth in this letter supersede all prior
agreements, understandings and representations between us concerning the subject
matter of this letter. Changes to your employment agreement would apply only if
in writing and signed by the Company's CEO. We look forward to you becoming a
member of our team!

Sincerely,

/s/ Philippe Pouletty

Philippe Pouletty
President

I, Maryvonne Hiance, understand and agree to the above terms. I understand that
my employment with DrugAbuse Sciences is at will, and I acknowledge that no
representations or promises other than those set forth above have been made to
me with regard to the terms and conditions of my employment.

Signed: /s/ Maryvonne Hiance                         Date:  June 9, 1999
       --------------------------------                    --------------------

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