HEALTHCARE ACQUISITION PARTNERS CORP.

Exhibit 4.1

UNIT(S) CONSISTING OF ONE SHARE OF COMMON STOCK AND TWO WARRANTS, EACH TO PURCHASE ONE SHARE OF COMMON STOCK

SEE REVERSE FOR CERTAIN DEFINITIONS

THIS CERTIFIES THAT                                                                                                                                                 IS THE OWNER OF                                                                                                                                                                                  UNIT(S). Each Unit (“Unit”) consists of one (1) share of common stock, par value $.0001 per share (“Common Stock”), of Healthcare Acquisition Partners Corp., a Delaware corporation (the “Corporation”), and two warrants (the “Warrants”). Each Warrant entitles the holder to purchase one (1) share of Common Stock for $5.00 per share (subject to adjustment). The Common Sock and Warrants comprising each Unit represented by this certificate are not transferable separately prior to                     , 2006, unless FTN Midwest Securities Corp. determines that an earlier date is acceptable. The terms of the Warrants are governed by a Warrant Agreement, dated as of                     , 2006 (the “Warrant Agreement”), between the Corporation and Mellon Investor Services LLC, as Warrant Agent, and are subject to the terms and provisions contained therein, all of which terms and provisions the holder of this certificate consents to by acceptance hereof. Copies of the Warrant Agreement are on file at the office of the Warrant Agent at Newport Office Center VII, 480 Washington Blvd., Jersey City, 07210, and are available to any Warrant holder on written request and without cost. This certificate is not valid unless countersigned by the Transfer Agent and registered by the Registrar of the Corporation.

WITNESS the seal of the Corporation and the facsimile signature of its duly authorized officers.

Dated:                     , 2006

[REVERSE]

The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations:

Additional abbreviations may also be used though not in the above list.

Healthcare Acquisition Partners Corp.

The Corporation will furnish without charge to each stockholder who so requests the powers, designations, preferences and relative, participating, option or other special rights of each class of stock or series thereof of the Corporation and the qualifications, limitations, or restrictions of such preferences and/or rights. This certificate and the Units represented hereby are issued and shall be held subject to the terms and conditions applicable to the securities underlying and comprising the Units.

For Value Received,                          hereby sell, assign and transfer unto

(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)

Units represented by the within Certificate, and do hereby irrevocably constitute and appoint                  Attorney, to transfer the said Units on the books of the within named Corporation with full power of substitution in the premises.