<PAGE>   1
                                                                   EXHIBIT 10.10


February 18, 1998

Mr. Alan Marquardt
3206 Belvedere Court
Pleasanton, CA  94588


Dear Alan:

The following sets forth the terms of your employment with UroQuest:

Position/Title:         VP - Regulatory and Clinical, Quality Affairs

Salary:                 Salary of $147,000 per annum to be reviewed at our
                        annual increase time of April 1 each year. This initial
                        salary will be your salary through April 1, 1999.

Bonus:                  30% (maximum) of salary based on objectives to be
                        mutually agreed upon. Such objectives will be a
                        combination of personal as well as corporate targets.
                        Your bonus for 1998 will be prorated based on the time
                        you spend working at UroQuest during 1998 and will be
                        guaranteed at 30% of your 1998 salary, subject to
                        proration.

Stock Options:          120,000 shares whose vesting will occur over a four (4)
                        year period commencing with your start of employment.
                        The price of those options will be based on the fair
                        market price at the date of grant, which date will
                        approximate your date of hire.

Vacation:               You will be entitled to two weeks per year. This will be
                        increased to three weeks at the completion of your fifth
                        year of service. You will be granted an additional six
                        weeks paid time off during 1998.

Benefits:               UroQuest will provide customary benefits such as
                        medical, dental and life insurance. Each employee will
                        be required to

<PAGE>   2

Mr. Alan Marquardt
February 18, 1998
Page 2 of 5


                        make certain contributions toward this coverage. In
                        addition, UroQuest sponsors a 401(K) plan that allows
                        each employee to contribute up to 15% of his or her
                        salary to the plan. The Company will match, at a 100%
                        rate, up to 4% of your salary contribution. You will
                        become eligible to participate in the 401(K) plan on
                        your one-year anniversary. You will also be eligible to
                        participate in the Company's Employee Stock Purchase
                        Plan.

Loan:                   You will be granted a $200,000 loan, interest free, at
                        the time you exercise your BSC options. Such loan will
                        be repayable at the end of 20 months. The loan will be
                        secured by sufficient shares of BSC stock at all times
                        to cover the loan balance (the Company and you will
                        execute a separate loan and security agreement to
                        formalize this arrangement). Per IRS guidelines you may
                        be subject to imputation of interest regarding this
                        loan.

Start Date:             March 2, 1998

Proprietary 
Information:            You agree to execute the Company's standard form of
                        employee proprietary information and inventions
                        agreement.

Resolution of 
Disputes;
Arbitration:            Any disputes between the parties relating in any way to
                        this Agreement, including without limitation, the
                        termination of your employment with UroQuest, shall be
                        resolved by arbitration.

Successors;
Entire Agreement:       This Agreement shall be binding upon any successor to
                        the Company, whether direct or indirect and whether by
                        purchase, lease, merger, consolidation, liquidation or
                        otherwise. The terms of this Agreement and all your
                        rights hereunder shall inure to the benefit of, and be
                        enforceable by, your personal or legal representatives,
                        executors, administrators, successors, heirs,
                        distributees, devisees and legatees. The terms of this
                        Agreement, including the terms of the proprietary
                        information and inventions agreement to be executed, are
                        intended by the parties to be the final expression of
                        their agreement with respect to your employment by the
                        Company and may not be contradicted by evidence of any
                        prior contemporaneous agreements. If
<PAGE>   3
Mr. Alan Marquardt
February 18, 1998
Page 3 of 5


                        any provision of this Agreement, or the application
                        thereof, shall be held to be invalid or unenforceable,
                        or void, the remainder of this Agreement shall remain in
                        full force and effect.

Amendment;
Governing Law:          This Agreement may not be amended or modified except by
                        writing signed by you and the Company. The terms of this
                        Agreement and the resolution of disputes shall be
                        governed by California Law.

At Will:                Employee's employment with the Company may be terminated
                        at any time, with or without good cause or for any or no
                        cause with or without notice.

Option Acceleration:    If your employment with the Company terminates as a
                        result of an Involuntary Termination other than for
                        Cause at anytime within twelve (12) months after a
                        Change of Control, then the vesting and exercisability
                        of each unvested option granted to you by the Company
                        (the "Options") shall be automatically accelerated in
                        full; provided, however, that if it is determined by the
                        Company's independent public accountants that such
                        acceleration would preclude accounting for the Change of
                        Control as a pooling of interests for financial
                        accounting purposes, and it is a condition to the
                        closing of the Change of Control that the transaction be
                        accounted for as a pooling of interests, then the
                        vesting and exercisability of the Options shall not
                        accelerate pursuant to this Section.

Definitions:            (a) Cause. "Cause" shall mean the occurrence of any one
                        or more of the following: (i) the Employee's conviction
                        by, or entry of a plea of guilty or nolo contender in, a
                        court of final jurisdiction for any crime which
                        constitutes a felony in the jurisdiction involved (other
                        than a felony traffic offense); (ii) the Employee's
                        misappropriation of funds or commission of a material
                        act of fraud, whether prior or subsequent to the date
                        hereof, upon the Company; (iii) gross negligence by the
                        Employee in the scope of the Employee's services to the
                        Company; (iv) a willful breach by the Employee of a
                        material provision of this Agreement; or (v) a willful
                        failure of the Employee to substantially perform his
                        duties hereunder. Notwithstanding the foregoing, the
                        Employee shall not be
<PAGE>   4
Mr. Alan Marquardt
February 18, 1998
Page 4 of 5


                        deemed to have been terminated for Cause under clause
                        (iii), (iv) or (v) of this Section 8(a) unless the
                        Company delivers a written notice to the Employee
                        setting forth the reasons for the Company's intention to
                        terminate for Cause and specifically identifying the
                        manner in which the Company believes that the Employee
                        has engaged in such conduct, which conduct is not
                        substantially corrected by the Employee within 10 days
                        following his receipt of such notice, and provides the
                        Employee with an opportunity, together with his counsel,
                        if any, to be heard by the Company.

                        (b) Change of Control. "Change of Control" shall mean
                        the occurrence of any of the following events:

                        (i) The approval by shareholders of the Company of a
                        merger or consolidation of the Company with any other
                        corporation, other than a merger or consolidation which
                        would result in the voting securities of the Company
                        outstanding immediately prior thereto continuing to
                        represent (either by remaining outstanding or by being
                        converted into voting securities of the surviving
                        entity) more than fifty percent (50%) of the total
                        voting power represented by the voting securities of the
                        Company or such surviving entity outstanding immediately
                        after such merger or consolidation;

                        (ii) Any approval by the shareholders of the Company of
                        a plan of complete liquidation of the Company or an
                        agreement for the sale or disposition by the Company of
                        all or substantially all of the Company's assets; or

                        (iii) Any "person" (as such term is used in Sections
                        13(d) and 14(d) of the Securities Exchange Act of 1934,
                        as amended) becoming the "beneficial owner" (as defined
                        in Rule 13d-3 under said Act), directly or indirectly,
                        of securities of the Company representing 50% or more of
                        the total voting power represented by the Company's then
                        outstanding voting securities.

                        (c) Involuntary Termination. "Involuntary Termination"
                        shall mean (i) without the Employee's express written
                        consent, a significant reduction of the Employee's
                        duties, position or responsibilities relative to the
                        Employee's duties, position or
<PAGE>   5
Mr. Alan Marquardt
February 18, 1998
Page 5 of 5


                        responsibilities in effect immediately prior to such
                        reduction, or the removal of the Employee from such
                        position, duties and responsibilities, unless the
                        Employee is provided with comparable duties, position
                        and responsibilities; provided, however, that a
                        reduction in duties, position or responsibilities solely
                        by virtue of the Company being acquired and made part of
                        a larger entity (as, for example, when the VP R&D of the
                        Company remains as such following a Change of Control
                        but is not made the VP R&D of the acquiring corporation)
                        shall not constitute an "Involuntary Termination" (ii) a
                        reduction by the Company of the Employee's base salary
                        as in effect immediately prior to such reduction; (iii)
                        a material reduction by the Company in the kind or level
                        of employee benefits to which the Employee is entitled
                        immediately prior to such reduction with the result that
                        the Employee's overall benefits package is significantly
                        reduced; (iv) without the Employee's express written
                        consent, the relocation of the Employee to a facility or
                        a location more than fifty (50) miles from his current
                        location; (v) any purported termination of the Employee
                        by the Company which is not effected for Cause or for
                        which the grounds relied upon are not valid; or (vi) the
                        failure of the Company to obtain the assumption of this
                        Agreement by any successors.


Sincerely,
UROQUEST MEDICAL CORPORATION

/s/ TERRY E. SPRAKER
Terry E. Spraker, Ph.D.
President and Chief Executive Officer


ACCEPTED:   /s/ ALAN MARQUARDT
            -------------------------
            Alan Marquardt