<PAGE>

                                                                     EXHIBIT 4.5

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, TRANSFERRED, ASSIGNED OR
HYPOTHECATED UNLESS THERE IS AN EFFECTIVE REGISTRATION STATEMENT UNDER SUCH ACT
COVERING SUCH SECURITIES, THE SALE IS MADE IN ACCORDANCE WITH RULE 144 UNDER THE
ACT, OR THE COMPANY RECEIVES AN OPINION OF COUNSEL FOR THE HOLDER OF THESE
SECURITIES REASONABLY SATISFACTORY TO THE COMPANY, STATING THAT SUCH SALE,
TRANSFER, ASSIGNMENT OR HYPOTHECATION IS EXEMPT FROM THE REGISTRATION AND
PROSPECTUS DELIVERY REQUIREMENTS OF SUCH ACT.

WC-___

                                 SANTARUS, INC.
                    SERIES C PREFERRED STOCK PURCHASE WARRANT

         THIS CERTIFIES THAT, for value received, _________________ ("Holder")
is entitled to purchase _________________ (_________________) shares of Series C
Preferred Stock of SANTARUS, INC., a California corporation (the "Company"), at
the Warrant Price (as defined in subsection 1(j) below), subject to adjustments
and all other terms and conditions set forth in this Warrant.

1. Definitions: As used herein, the following terms, unless the context
otherwise requires, shall have the following meanings:

         (a) "Act" shall mean the Securities Act of 1933, as amended, or any
successor federal statute, and the rules and regulations of the Commission
thereunder, all as the same shall be in effect at the time.

         (b) "Articles of Incorporation" shall mean the Company's Amended and
Restated Articles of Incorporation in the form filed with the California
Secretary of State in connection with the Company's Series C Preferred Stock
Financing.

         (c) "Commission" shall mean the Securities and Exchange Commission, or
any other federal agency at the time administering the Act.

         (d) "Company" shall mean SANTARUS, INC., a California corporation, and
any corporation which shall succeed to or assume the obligations of SANTARUS,
INC., under this Warrant.

         (e) "Date of Grant" shall mean _________________, 20__.

         (f) "Exercise Date" shall mean the effective date of the delivery of
the Notice of Exercise pursuant to Sections 3 and 10 below.

                                       1
<PAGE>
         (g) "Holder" shall mean Holder or any other person or entity who shall
at the time be the registered holder of this Warrant.

         (h) "Series, C Preferred Stock" shall mean shares of the, Company's
Series C Preferred Stock to be authorized after the Date of Grant upon the
filing by the Company of the Articles of Incorporation.

         (i) "Series C Preferred Stock Financing" shall mean the Company's
issuance of shares of Series C Preferred Stock to the Holder and the other
persons participating therein in a transaction, or series of related
transactions, in which the Company receives gross proceeds of at least
$13,000,000.

         (j) "Warrant Price" shall mean $____ per share.

         (k) "Warrant Shares" shall mean shares of the Company's Series C
Preferred Stock; provided, however, in the event of the automatic conversion of
the Company's outstanding Series C Preferred Stock into Common Stock pursuant to
the provisions of the Company's current charter documents or the Articles of
Incorporation, then, effective upon such conversion, "Warrant Shares" shall
thereafter mean shares of the Company's Common Stock.

2. Term. The purchase right represented by this Warrant is exercisable during
the period commencing upon the earlier of (a) the Company's filing of the
Articles of Incorporation with the California Secretary of State and (b)
_________________, 20__, and ending on _________________, 20__. The foregoing
notwithstanding, in the event of the Acquisition of the Company prior to the
occurrence of (a) and (b) in the preceding sentence, then the purchase right
represented by this Warrant shall be exercisable immediately prior to, and shall
terminate immediately after, the consummation of such Acquisition.

3. Exercise of Warrant.

         (a) Exercise. This Warrant may be exercised, in whole or in part, by
the Holder hereof by surrender of this Warrant, with the form of subscription at
the end hereof duly executed by the Holder, to the Company at its principal
office, accompanied by payment of the Warrant Price in cash or by certified or
official bank check payable to the order of the Company.

         (b) Right to Convert Warrant. Notwithstanding the payment provisions of
subsection 3(a) hereof:

            (i) The Holder shall have the right (the "Conversion Right") to
require the Company to convert this Warrant, in whole or in part, at any time
into Warrant Shares as provided for in this subsection (b). At the sole option
of the Holder, upon exercise of the Conversion Right, the Company shall deliver
to the Holder (without payment by the Holder of any Warrant Price) that number
of Warrant Shares equal to the quotient obtained by dividing (x) the value of
the Warrant at the time the Conversion Right is exercised (determined by
subtracting the aggregate Warrant Price for the number of Warrant Shares then
issuable upon exercise of this Warrant in effect immediately prior to the
exercise of the Conversion Right from the aggregate Fair Market Value (as
defined below) of such number of Warrant Shares immediately prior to

                                       2
<PAGE>
the exercise of the Conversion Right) by (y) the Fair Market Value of one
Warrant Share immediately prior to the exercise of the Conversion Right.

            (ii) The Conversion Right may be exercised by the Holder, at any
time, or from time to time, on any business day by delivering a written notice
(the "Conversion Notice") to the Company exercising the Conversion Right and
specifying (i) the total number of Warrant Shares the Holder will purchase
pursuant to such conversion and (ii) a place and date not less than one nor more
than 20 business days from the date of the Conversion Notice for the closing of
such purchase.

            (iii) Fair Market Value of a Warrant Share as of a particular date
(the "Determination Date") shall mean:

                  (1) If the Company's Warrant Shares are traded on an exchange
or are quoted on the Nasdaq National Market, then the closing or last sale
price, respectively, reported for the last business day immediately preceding
the Determination Date.

                  (2) If the Company's Warrant Shares are not traded on an
exchange or on the Nasdaq National Market but are traded in the over-the-counter
market, then the mean of the closing bid and asked prices reported for the last
business day immediately preceding the Determination Date.

                  (3) If the Company's Warrant Shares are not publicly traded,
then as determined in good faith by the Company's Board of Directors upon review
of relevant factors.

         (c) Delivery of Certificate. In the event of any exercise of the
purchase right represented by this Warrant, certificates for the Warrant Shares
so purchased shall be delivered to the Holder within thirty (30) days of
delivery of the notice of exercise (the "Notice of Exercise") in the form of
Exhibit A attached hereto and, unless this Warrant has been fully exercised or
has expired, a new warrant representing the portion of the Warrant Shares with
respect to which this Warrant shall not then have been exercised shall also be
issued to the Holder within such thirty (30) day period.

         (d) No Fractional Shares. No fractional shares shall be issued in
connection with any exercise hereunder, but in lieu of such fractional shares
the Company shall make a cash payment therefor upon the basis of the Fair Market
Value of a Warrant Share as of the Exercise Date.

         (e) Company's Representations.

            (i) All Warrant Shares which may be issued upon the exercise of the
purchase right represented by this Warrant shall, upon issuance, be duly
authorized, validly issued, fully paid and nonassessable, and free of any liens
and encumbrances except for restrictions on transfer provided for herein or
under applicable federal and state securities laws. During the period within
which the purchase right represented by this Warrant may be exercised, the
Company shall at all times have authorized, and reserved for the purpose of
issuance upon exercise of the purchase right represented by this Warrant, a
sufficient number of Warrant Shares to provide for the exercise of the purchase
right represented by this Warrant;

                                       3
<PAGE>
            (ii) This Warrant has been duly authorized and executed by the
Company and is a valid and binding obligation of the Company enforceable in
accordance with its terms, subject to applicable bankruptcy, insolvency,
reorganization, moratorium or other laws of general application affecting the
enforcement of creditors' rights;

            (iii) The execution and delivery of this Warrant are not, and the
issuance of the Warrant Shares upon exercise of this Warrant in accordance with
the terms hereof will not be inconsistent with the Company's Articles of
Incorporation or Bylaws, do not and will not contravene any law, governmental
rule or regulation, judgment or order applicable to the Company, and do not and
will not conflict with or contravene any provision of, or constitute a material
default under, any material indenture, mortgage, contract or other instrument of
which the Company is a party or by which it is bound or require the consent or
approval of, the giving of notice to, the registration or filing with or the
taking of any action in respect of or by, any federal, state or local government
authority or agency (other than such consents, approvals, notices, actions,
filings, etc., as have already been obtained or made, as the case may be).

4. Adjustment of Warrant Price and Number of Warrant Shares. The number of
Warrant Shares issuable upon the exercise of this Warrant and the Warrant Price
shall be subject to adjustment from time to time upon the occurrence of certain
events, as follows:

         (a) Adjustment for Dividends in Stock. In case at any time or from time
to time the holders of Warrant Shares of the Company (or any shares of stock or
other securities at the time receivable upon the exercise of this Warrant) shall
have received or, on or after the record date fixed for the determination of
eligible stockholders, shall have become entitled to receive, without payment
therefor, other or additional stock of the Company by way of dividend then, and
in each case, the Holder of this Warrant shall, upon the exercise hereof, be
entitled to receive, in addition to the number of Warrant Shares receivable
thereupon, and without payment of any additional consideration therefor, the
amount of such other or additional stock of the Company which such Holder would
hold on the date of such exercise had it been the holder of record of Warrant
Shares on the date hereof and had thereafter, during the period from the date
hereof to and including the date of such exercise, retained such shares and/or
all other additional stock receivable by it as aforesaid during such period,
giving effect to all adjustments called for during such period by subparagraphs
(b) and (c) of this Paragraph 4.

         (b) Adjustment for Reclassification or Reorganization. In case of any
reclassification or change of the outstanding Warrant Shares of the Company or
of any reorganization of the Company, then and in each such case the Holder of
this Warrant, upon the exercise hereof at any time after the consummation of
such reclassification, change, or reorganization, shall be entitled to receive,
in lieu of or in addition to the stock or other securities and property
receivable upon the exercise hereof prior to such consummation, the stock or
other securities to which such Holder would have been entitled upon such
consummation if such Holder had exercised this Warrant immediately prior
thereto, all subject to further adjustment as provided in subparagraphs (a) and
(c); in each such case, the terms of this Paragraph 4 shall be applicable to the
shares. of stock or other securities and property receivable upon the exercise
of this Warrant after such consummation.

                                       4
<PAGE>
         (c) Stock Splits and Reverse Stock Splits. If the Company shall
subdivide its outstanding Warrant Shares into a greater number of shares, the
Warrant Price in effect immediately prior to such subdivision shall thereby be
proportionately reduced and the number of Warrant Shares receivable upon
exercise of this Warrant shall thereby be proportionately increased; and,
conversely, if the outstanding number of Warrant Shares shall be combined into a
smaller number of shares, the Warrant Price in effect immediately prior to such
combination shall thereby be proportionately increased and the number of Warrant
Shares receivable upon exercise of the Warrant shall be proportionately
decreased.

5. Notices of Record Date, Etc. In the event of (a) any taking by the Company of
a record of the holders of any class of securities for the purpose of
determining the holders thereof who are entitled to receive any dividend or
other distribution (the "Distribution"), (b) any capital reorganization or
reclassification of the stated capital of the Company or any consolidation or
merger of the Company with any other corporation or corporations (other than a
wholly-owned subsidiary), or the sale or distribution of all or substantially
all of the Company's property and assets (the "Reorganization Event"), or (c)
any proposed filing of a registration statement under the Act in connection with
a primary public offering of the Company's Common Stock (the "Registration
Event"), the Company will mail or cause to be mailed to the Holder a notice
specifying (i) the date of any such Distribution stating the amount and
character of such Distribution, (ii) the date on which any such Reorganization
Event or Registration Event is expected to become effective, and (iii) the time,
if any, that is to be fixed as to when the holders of record of the Company's
securities shall be entitled to exchange their shares of the Company's
securities for securities or other property deliverable upon such Reorganization
Event. Such notice shall be mailed at least thirty (30) days prior to the date
therein specified.

6. Compliance with Act; Transferability and Negotiability of Warrant;
Disposition of Shares.

         (a) Compliance with Act. The Holder, by acceptance hereof, agrees that
this Warrant and the Warrant Shares to be issued upon the exercise hereof are
being acquired solely for its own account and not as a nominee for any other
party and not with a view toward the resale or distribution thereof and that it
will not offer, sell or otherwise dispose of this Warrant or any Warrant Shares
to be issued upon the exercise hereof except under circumstances which will not
result in a violation of the Act. Upon the exercise of this Warrant, the Holder
shall confirm in writing, in a form satisfactory to the Company, that the
Warrant Shares so issued are being acquired solely for its own account and not
as a nominee for any other party and not with a view toward resale or
distribution thereof in violation of the Act. This Warrant and the Warrant.
Shares to be issued upon the exercise hereof (unless registered under the Act
and unless, in the case of the Warrant Shares, such Shares may thereupon be sold
pursuant to Commission Rule 144(k)) shall be imprinted with a legend in
substantially the following form:

         THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
         SECURITIES ACT OF 1933, AS AMENDED AND MAY NOT BE SOLD, TRANSFERRED,
         ASSIGNED OR HYPOTHECATED UNLESS THERE IS AN EFFECTIVE REGISTRATION
         STATEMENT UNDER SUCH ACT COVERING SUCH SECURITIES, THE SALE IS MADE IN
         ACCORDANCE WITH RULE 144 UNDER THE ACT, OR

                                       5
<PAGE>
         THE COMPANY RECEIVES AN OPINION OF COUNSEL FOR THE HOLDER OF THESE
         SECURITIES REASONABLY SATISFACTORY TO THE COMPANY. STATING THAT SUCH
         SALE, TRANSFER, ASSIGNMENT OR HYPOTHECATION IS EXEMPT FROM THE
         REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SUCH ACT.

         In addition, this Warrant and the Warrant Shares to be issued upon the
exercise hereof shall bear any legends required by the securities laws of any
applicable states.

         (b) Transferability and Negotiability of Warrant. This Warrant may not
be transferred or assigned in whole or in part without compliance with all
applicable federal and state securities laws by the transferor and the
transferee (including the delivery of investment representation letters and
legal opinions reasonably satisfactory to the Company, if requested by the
Company and the transfer is to a person other than a general partner of the
initial Holder). Subject to the provisions of this Warrant with respect to
compliance with the Act, title to this Warrant may be transferred by endorsement
and delivery in the same manner as a negotiable instrument transferable by
endorsement and delivery. The Company shall act promptly to record transfers of
this Warrant on its books, but the Company may treat the registered holder of
this Warrant as the absolute owner of this Warrant for all purposes,
notwithstanding any notice to the contrary.

         (c) Disposition of Warrant Shares. With respect to any offer sale,
transfer or other disposition of any Warrant Shares acquired pursuant to the
exercise of this Warrant prior to registration of such Warrant Shares, except
for any such offer, sale, transfer or other disposition of Warrant Shares to a
partner of the initial Holder, the Holder and each subsequent holder of this
Warrant agrees to give written notice to the Company prior thereto, describing
briefly the manner thereof, together with a written opinion of legal counsel for
such holder, reasonably satisfactory to the Company and its legal counsel, if
requested by the Company, to the effect that such offer, sale or other
disposition may be effected without registration or qualification (under the Act
or any other federal or state securities laws) of such Warrant Shares and
indicating whether or not under the Act, certificates for such Warrant Shares to
be sold or otherwise disposed of require any restrictive legend as to the
applicable restrictions on transferability in order to ensure compliance with
the Act. Promptly upon receiving such written notice and reasonably satisfactory
opinion, if so requested, the Company, as promptly as practicable, shall notify
such holder that such holder may sell or otherwise dispose of such Warrant
Shares, all in accordance with the terms of the notice delivered to the Company.
If a determination has been made pursuant to this subsection (c) that the
opinion of legal counsel for the holder is not reasonably satisfactory to the
Company and its legal counsel, the Company shall so notify the holder promptly
after such determination has been made. Notwithstanding the foregoing, such
Warrant Shares may be offered, sold or otherwise disposed of in accordance with
Rule 144, provided that the Company shall have been furnished with such
information as the Company may reasonably request to provide a reasonable
assurance that the provisions of Rule 144 have been satisfied. Each certificate
representing the Warrant Shares thus transferred (except a transfer pursuant to
Rule l44(k) or an effective registration statement) shall bear a restrictive
legend as to the applicable restrictions on transferability in order to ensure
compliance with the Act, unless in the aforesaid opinion of legal counsel for
the holder, such legend is not required in

                                       6
<PAGE>
order to ensure compliance with the Act. The Company may issue stop transfer
instructions to its transfer agent in connection with such restrictions

7. Rights of Stockholders. No Holder shall be entitled to vote or receive
dividends or be deemed the holder of Warrant Shares or any other securities of
the Company which may at any time be issuable on the exercise of this Warrant
for any purpose, nor shall anything contained herein be construed to confer upon
the Holder, as such, any of the rights of a stockholder of the Company or any
right to vote for the election of directors or upon any matter submitted to
stockholders at any meeting thereof, or to give or withhold consent to any
corporate action (whether upon any recapitalization, issuance of stock,
reclassification of stock, consolidation, merger, transfer of assets or
otherwise) or to receive notice of meetings, or to receive dividends or
subscription rights or otherwise until this Warrant shall have been exercised
and the Warrant Shares issuable upon exercise hereof shall have become
deliverable, as provided herein.

8. Replacement of Warrants. On receipt of evidence reasonably satisfactory to
the Company of the loss, theft, destruction or mutilation of this Warrant and,
in the case of loss, theft or destruction, on delivery of an indemnity agreement
reasonably satisfactory in form and amount to the Company or, in the case of
mutilation, on surrender and cancellation of this Warrant, the Company at its
expense shall execute and deliver, in lieu of this Warrant, a new warrant of
like tenor.

9. Exchange of Warrant. Subject to the other provisions of this Warrant, on
surrender of this Warrant for exchange, properly endorsed and subject to the
provisions of this Warrant with respect to compliance with the Act, the Company
at its expense shall issue to or on the order of the Holder a new warrant or
warrants of like tenor, in the name of the Holder or as the Holder (on payment
by the Holder of any applicable transfer taxes) may direct, for the number of
Warrant Shares issuable upon exercise thereof.

10. Notices. All notices and other communications from the Company to the
Holder, or vice versa, shall be deemed delivered and effective when given
personally or three days after being mailed by first-class registered or
certified mail, postage prepaid, at such address as may have been furnished to
the Company or the Holder, as the case may be, in writing by the Company or such
Holder from time to time.

11. Waiver. This Warrant and any term hereof may be changed, waived, discharged
or terminated only by an instrument in writing signed by the party against which
enforcement of such change, waiver, discharge or termination is sought.

12. Governing Law. This Warrant shall be governed by and construed in accordance
with the Laws of the State of California, as such laws are applied to agreements
entered into in California and to be performed solely by California residents.

13. Titles and Subtitles; Forms of Pronouns. The titles of the Sections and
Subsections of this Warrant are for convenience only and are not to be
considered in construing this Warrant. All pronouns used in this Warrant shall
be deemed to include masculine, feminine and neuter forms.

                                       7
<PAGE>
14. Expiration. Subject to the provisions of Section 2 above, the right to
exercise this Warrant shall expire at 5:00 P.M. California time, on
_________________, 20__.

Dated: _________________

                                                     SANTARUS, INC.

                                                     By:____________________


                                       8
<PAGE>
                                    EXHIBIT A

                               NOTICE OF EXERCISE
                   (To be signed only on exercise of Warrant)


TO:      SANTARUS, INC.

         The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise this Warrant for, and to purchase thereunder, ________ shares
of Series C Preferred Stock of Santarus, Inc. and herewith makes payment of
$__________ therefor (either in cash or in accordance with the cashless exercise
provisions of Section 3(b))and requests that the certificates for such shares be
issued in the name of, and delivered to __________________________ whose address
is
______________________________________________________________________________




Dated:_____________________                ________________________________
                                           (Signature must conform to name of
                                           holder as specified on the face of
                                           the Warrant)

                                           ________________________________
                                           (Name)

                                           ________________________________
                                           (Address)


Schedule to Exhibit 4.5

The preceding form of Series C Preferred Stock Purchase Warrant of the Company
was issued to the following entities on the dates and in the amounts listed
below:

(i) the Hale Family Trust, issued on December 21, 2000, and
January 17, 2001, and exercisable in the aggregate for 32,920 shares of
our Series C Preferred Stock, (ii) St. Paul Venture Capital V, LLC,
issued on October 23, 2000, November 3, 2000, November 28, 2000 and
February 1, 2001, and exercisable in the aggregate for 70,368 shares of
our Series C Preferred Stock and (iii) Fog City Fund, LLC, issued on
January 30, 2001, and exercisable for 41,152 shares of our Series C
Preferred Stock.  Each of the warrants set forth above is exercisable at
a price per share of $2.43.