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                                                                     EXHIBIT 4.5

                         BONE CARE INTERNATIONAL, INC.
                            1996 STOCK OPTION PLAN
           (as amended through November 15, 2000 and reflecting the
              2-for-1 stock split distributed November 14, 1997)

     1.  Plan.  To provide incentives to officers, key employees and consultants
         ----
of Bone Care International, Inc. (the "Company") and its subsidiaries from time
to time, and members of the Board of Directors of the Company (the "Board") to
contribute to the success and prosperity of the Company, based upon the
ownership of the common stock, no par value, of the Company ("Common Stock"),
the Committee hereinafter designated, may grant nonqualified stock options to
officers, key employees, consultants and eligible members of the Board on the
terms and subject to the conditions stated in this Plan.

     2.  Eligibility.  Officers, key employees and consultants of the Company
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and its subsidiaries and members of the Board who are not employees of the
Company ("non-employee directors") shall be eligible, upon selection by the
Committee, to receive stock options as the Committee, in its discretion, shall
determine.

     3.  Shares Issuable.  The maximum number of shares of Common Stock to be
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available under this Plan pursuant to all grants of stock options hereunder
shall be 1,600,000, subject to adjustment in accordance with Section 5. Shares
of Common Stock subject to a stock option granted hereunder, which are not
issued by reason of expiration, cancellation or other termination of such stock
option, shall again be available for future grants of stock options under this
Plan; provided, however, that except for appropriate adjustments made to give
effect to any stock splits, stock dividends or other relevant changes in the
capitalization of the Corporation, without the approval by a majority vote of
the shareholders, shares subject to an outstanding stock option that is
replaced, canceled or exchanged for a newly granted stock option with an option
price per share lower than the option price per share of the outstanding stock
option shall not be available for future grants.

     Shares of Common Stock to be issued may be authorized and unissued shares
of Common Stock, treasury stock, or a combination thereof.

     To the extent required by Section 162(m) of the Internal Revenue Code of
1986, as amended (the "Code"), and the rules and regulations thereunder, the
maximum number of shares of Common Stock with respect to which options may be
granted during any calendar year to any person shall be 200,000, subject to
adjustment as provided in Section 5.

     4.  Administration of the Plan.  The Plan shall be administered by a
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committee designated by the Board, which may be the whole Board (the
"Committee"), or may consist of two or more members of the Board, each of whom
may be a "Non-Employee Director," within the meaning of Rule 16b-3 under the
Securities Exchange Act of 1934,
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as amended (the "Exchange Act"), and an "outside director" within the meaning of
Section 162(m) under the Code.

     The Committee shall, subject to the terms of this Plan, establish
eligibility guidelines, select officers, key employees, consultants and non-
employee directors for participation in this Plan and determine the number of
shares of Common Stock subject to a stock option granted hereunder, the exercise
price for such shares of Common Stock, the time and conditions of vesting or
exercise and all other terms and conditions of the stock option, including,
without limitation, the form of the option agreement.  The Committee may
establish rules and regulations for the administration of the Plan, interpret
the Plan and impose, incidental to the grant of a stock option, conditions with
respect to the grant or award of stock options or competitive employment or
other activities not inconsistent with or conflicting with this Plan.  All such
rules, regulations and interpretations relating to this Plan adopted by the
Committee shall be conclusive and binding on all parties.  All grants of stock
options under this Plan shall be evidenced by written agreements between the
Company and the optionees, and no such grant shall be valid until so evidenced.

     5.  Changes in Capitalization.  Appropriate adjustments shall be made by
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the Committee in the maximum number of shares to be issued under the Plan and
the maximum number of shares which are subject to any stock option granted
hereunder, and the exercise price therefor, to give effect to any stock splits,
stock dividends and other relevant changes in the capitalization of the Company
occurring after the effective date of this Plan (which shall not include the
sale by the Company of shares of Common Stock or securities convertible into
shares of Common Stock).

     6.  Effective Date and Term of Plan.  This Plan shall be submitted to the
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shareholders of the Company for approval and, if approved, shall become
effective on the date thereof; provided, however, that this Plan and any options
granted hereunder shall be null and void in the event the Company's registration
statement under Section 12 of the Exchange Act does not become effective on or
prior to December 31, 1996.  This Plan shall terminate ten years after it
becomes effective unless terminated prior thereto by action of the Board.  No
further grants shall be made under this Plan after termination, but termination
shall not affect the rights of any optionee under any grants made prior to
termination.

     7.  Amendments.  This Plan may be amended by the Board in any respect,
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except that no amendment may be made without shareholder approval if such
amendment would (a) increase the maximum number of shares of Common Stock
available for issuance under this Plan (other than as provided in Section 5),
(b) amend the first paragraph of Section 3 to permit shares subject to an
outstanding stock option that is replaced, canceled or exchanged for a newly
granted stock option with an option price per share lower than the option price
per share of the outstanding stock option to become available for future grants,
or (c) otherwise require shareholder approval.
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     8.  Grants of Stock Options.  Options to purchase shares of Common Stock
         -----------------------
may be granted hereunder to such eligible officers, key employees, consultants,
and non-employee directors as may be selected by the Committee.

     9.  Option Price.  The option price per share of Common Stock purchasable
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upon exercise of an option granted hereunder shall be determined by the
Committee; provided, however, that the option price per share of Common Stock
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purchasable upon exercise of an option grant under this Plan shall be 100% of
the fair market value of a share of Common Stock on the date of grant of such
option.  For purposes hereof, "fair market value" shall be determined by the
Committee.

     10. Stock Option Period.  Each stock option granted hereunder may be
         -------------------
granted at any time on or after the effective date, and prior to the
termination, of this Plan.  The Committee shall determine whether such stock
option shall become exercisable in cumulative or non-cumulative installments or
in full at any time.  An exercisable stock option may be exercised in whole or
in part with respect to whole shares of Common Stock only.  The period for the
exercise of each stock option shall be determined by the Committee.

     11. Exercise of Stock Options.  (a) Upon exercise, the option price may be
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paid in cash, in previously owned shares of Common Stock (which the optionee has
held for at least six months or acquired on the open market and which the
optionee owns free and clear from all encumbrances) having a fair market value
on the date of exercise equal to the option price, or in a combination thereof.
The Company may arrange or approve of a cashless option exercise procedure which
complies with the provisions of Section 16 of the Exchange Act and the rules and
regulations thereunder.

     (b) Unless otherwise specified in the agreement relating to an option, an
option may be exercised during an optionee's continued employment with the
Company or one of its subsidiaries, or service on the Board, as the case may be,
within the 30-day period following termination of such employment or service,
but only to the extent exercisable and within the term of such option at the
time of the termination of such employment or service; provided, however, that,
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unless otherwise specified in the agreement relating to an option, if employment
of the optionee by the Company or one of its subsidiaries or service on the
Board shall have terminated by reason of death or retirement after age 60, then
the option may be exercised within the one-year period following such
termination of employment or service on the Board by the optionee or the
executor, administrator, personal representative, beneficiary or heir of the
optionee, but only to the extent exercisable and within the term of such option
at the time of such termination of employment or service.

     (c) Unless otherwise specified in the agreement relating to an option, if
an optionee dies during the 30-day period or one-year period set forth in
Section 11(b) (or other period set forth in the agreement relating to an
option), each option held by the optionee shall be exercisable only to the
extent exercisable and within the term of such option at the date of the
optionee's death and may thereafter be exercised by the executor,
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administrator, personal representative, beneficiary or heir of the optionee
within the one-year period following the date of the optionee's death.

     (d)  Unless otherwise specified in the agreement relating to an option, no
option shall be transferable other than by will or the laws of descent and
distribution or pursuant to beneficiary designation procedures approved by the
Company.  Except to the extent permitted by the foregoing sentence, each option
may be exercised during the optionee's lifetime only by the optionee or the
optionee's legal representative or similar person.  Except as permitted by the
second preceding sentence, no option hereunder shall be sold, transferred,
assigned, pledged, hypothecated, encumbered or otherwise disposed of (whether by
operation of law or otherwise) or be subject to execution, attachment or similar
process.  Upon any attempt to so sell, transfer, assign, pledge, hypothecate,
encumber or otherwise dispose of any option hereunder, such option and all
rights thereunder shall immediately become null and void.

     12.  Acceleration of Options upon a Change in Control.  The following
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provisions shall apply in the event of a "Change in Control":

     (a)  In the event of a Change in Control, any stock options not previously
exercisable in full shall become fully exercisable.

     (b)  For purposes hereof, "Change in Control" means:

     (1)  The acquisition by any individual, entity or group (a "Person"),
including any "person" within the meaning of Section 13(d)(3) or 14(d)(2) of the
Exchange Act, of beneficial ownership within the meaning of Rule 13d-3
promulgated under the Exchange Act, of 50% or more of the then outstanding
shares of Common Stock (the "Outstanding Common Stock"); provided, however, that
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the following acquisitions shall not constitute a Change in Control:  (A) any
acquisition by the Company, (B) any acquisition by an employee benefit plan (or
related trust) sponsored or maintained by the Company or any corporation
controlled by the Company, (C) any acquisition by an underwriter or underwriters
as part of a bona fide public distribution of securities of the Company or (D)
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any acquisition by any Person which beneficially owned as of the effective date
of this Plan, 30% or more of the outstanding Common Stock; and provided further
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that, for purposes of clause (A), if any Person (other than the Company or any
employee benefit plan (or related trust) sponsored or maintained by the Company
or any corporation controlled by the Company) shall become the beneficial owner
of 50% or more of the outstanding Common Stock by reason of an acquisition by
the Company and such Person shall, after such acquisition by the Company, become
the beneficial owner of any additional shares of the Outstanding Common Stock
and such beneficial ownership is publicly announced, such additional beneficial
ownership shall constitute a Change in Control;

     (2)  Individuals who, as of the date hereof, constitute the Board (the
"Incumbent Board") cease for any reason to constitute at least a majority of
such Board; provided, however, that any individual who becomes a director of the
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Company subsequent to the date hereof whose election, or nomination for election
by the Company's shareholders,
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was approved by the vote of at least a majority of the directors then comprising
the Incumbent Board shall be deemed to have been a member of the Incumbent
Board; and provided further, that no individual who was initially elected as a
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director of the Company as a result of an actual or threatened election contest,
as such terms are used in Rule 14a-11 of Regulation 14A promulgated under the
Exchange Act, or any other actual or threatened solicitation of proxies or
consents by or on behalf of any Person other than the Board shall be deemed to
have been a member of the Incumbent Board;

     (3) Approval by the shareholders of the Company of a reorganization, merger
or consolidation unless, in any such case, immediately after such
reorganization, merger or consolidation, (i) more than 50% of the then
outstanding shares of common stock of the corporation resulting from such
reorganization, merger or consolidation and more than 50% of the combined voting
power of the then outstanding securities of such corporation entitled to vote
generally in the election of directors is then beneficially owned, directly or
indirectly, by all or substantially all of the individuals or entities who were
the beneficial owners, respectively, of the Outstanding Common Stock immediately
prior to such reorganization, merger or consolidation and in substantially the
same proportions relative to each other as their ownership, immediately prior to
such reorganization, merger or consolidation, of the Outstanding Common Stock,
(ii) no Person (other than the Company, any employee plan (or related trust)
sponsored or maintained by the Company or the corporation resulting from such
reorganization, merger or consolidation (or any corporation controlled by the
Company) and any Person which beneficially owned, immediately prior to such
reorganization, merger or consolidation, directly or indirectly, 30% or more of
the Outstanding Common Stock) beneficially owns, directly or indirectly, 50% or
more of the then outstanding shares of common stock of such corporation or 50%
or more of the combined voting power of the then outstanding securities of such
corporation entitled to vote generally in the election of directors and (iii) at
least a majority of the members of the board of directors of the corporation
resulting from such reorganization, merger or consolidation were members of the
Incumbent Board at the time of the execution of the initial agreement or action
of the Board providing for such reorganization, merger or consolidation; or

     (4) Approval by the shareholders of the Company of (i) a plan of complete
liquidation or dissolution of the Company or (ii) the sale or other disposition
of all or substantially all of the assets of the Company other than to a
corporation with respect to which, immediately after such sale or other
disposition, (A) more than 50% of the then outstanding shares of common stock
thereof and more than 50% of the combined voting power of the then outstanding
securities thereof entitled to vote generally in the election of directors is
then beneficially owned, directly or indirectly, by all or substantially all of
the individuals and entities who were the beneficial owners, respectively, of
the Outstanding Common Stock immediately prior to such sale or other disposition
and in substantially the same proportions relative to each other as their
ownership, immediately prior to such sale or other disposition, of the
Outstanding Common Stock, (B) no Person (other than the Company, any employee
benefit plan (or related trust) sponsored or maintained by the Company or such
corporation (or any corporation controlled by the Company) and any Person which
beneficially owned, immediately prior to such sale or other disposition,
directly or indirectly, 30% or more of the Outstanding Common Stock)
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beneficially owns, directly or indirectly, 50% or more of the then outstanding
shares of common stock thereof or 50% or more of the combined voting power of
the then outstanding securities thereof entitled to vote generally in the
election of directors and (C) at least a majority of the members of the board of
directors thereof were members of the Incumbent Board at the time of the
execution of the initial agreement or action of the Board providing for such
sale or other disposition.