<PAGE>

                                                                    Exhibit 10.4

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                       NEXMED (U.S.A.), INC., AS MORTGAGOR

                                       AND

          THE TAIL WIND FUND LTD. AND SOLOMON STRATEGIC HOLDINGS, INC.,
                           COLLECTIVELY AS MORTGAGEE


                -------------------------------------------------


                               FIRST AMENDMENT OF
                        MORTGAGE, SECURITY AGREEMENT AND
                         ASSIGNMENT OF LEASES AND RENTS


                                      (FEE)


                -------------------------------------------------

                      DATED:     AS OF DECEMBER 12, 2003

                      LOCATION:  89 TWIN RIVERS DRIVE
                                 EAST WINDSOR, NEW JERSEY 08520


        The premises described within this instrument are also known as:

                      Block 20.06
                      Lot 6

        on the Official Tax Map of the Township of East Windsor, Mercer
        County, New Jersey


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                              RECORD AND RETURN TO:

                             Peter J. Weisman, P.C.
                               335 Madison Avenue
                                   Suite 1702
                            New York, New York 10017
                          Attn: Peter J. Weisman, Esq.


<PAGE>

                          FIRST AMENDMENT OF MORTGAGE,
              SECURITY AGREEMENT AND ASSIGNMENT OF LEASES AND RENTS


         THIS FIRST AMENDMENT OF MORTGAGE, SECURITY AGREEMENT AND ASSIGNMENT OF
LEASES AND RENTS (this "Amendment") is made as of the 12th day of December,
2003, between, on the one hand, NEXMED (U.S.A.), INC., a Delaware corporation
having its principal place of business at 350 Corporate Boulevard, Robbinsville,
NJ 08691 (the "Mortgagor"), and, on the other hand, THE TAIL WIND FUND LTD., a
British Virgin Islands limited liability company having an address at c/o Tail
Wind Advisory and Management Ltd., Attn: David Crook, 1st Floor, No. 1 Regent
Street, London, SW1Y 4NS UK ("Tail Wind"), SOLOMON STRATEGIC HOLDINGS, INC., a
British Virgin Islands limited liability company ("Solomon") (Tail Wind and
Solomon, collectively, the "Mortgagee"), and Tail Wind, in its capacity as the
collateral agent for the Mortgagee.


                               W I T N E S S E T H


         WHEREAS, the Mortgagor is the owner of a fee estate in the real
property described in Exhibit A attached hereto and made a part hereof and
commonly known as 89 Twin Rivers Drive, East Windsor, New Jersey 08520 (the
"Premises");

         WHEREAS, the Mortgagor is a wholly-owned subsidiary of NexMed, Inc., a
Nevada corporation (the "Parent");

         WHEREAS, the Mortgagee is the owner and holder of that certain
Mortgage, Security Agreement and Assignment of Leases and Rents, dated as of
June 11, 2002, made by the Mortgagor in favor of the Mortgagee and recorded June
19, 2002, in the Mercer County Clerk's Office, in Book 7091, Page 020 (the
"Original Mortgage"), which instrument covers (inter alia) the fee estate of the
Mortgagor in and to the Premises;

         WHEREAS, the Original Mortgage was given by the Mortgagor to the
Mortgagee to secure (inter alia) (i) the obligations of the Mortgagor under that
certain Subsidiary Guaranty, dated as of June 11, 2002, made by the Mortgagor in
favor of the Mortgagee, (ii) the obligations of the Parent under that certain 5%
Convertible Note Due November 30, 2005, dated June 11, 2002, from the Parent to
Tail Wind, and (iii) the obligations of the Parent under that certain 5%
Convertible Note Due November 30, 2005, dated June 11, 2002, from the Parent to
Solomon;

         WHEREAS, simultaneously with the execution and delivery hereof, the
Parent and the Mortgagee are executing and delivering that certain Purchase
Agreement, dated as of the date hereof ("New Purchase Agreement");

<PAGE>

         WHEREAS, pursuant to the New Purchase Agreement, (i) Tail Wind,
simultaneously with the execution and delivery hereof, is purchasing from the
Parent that certain 5% Convertible Note Due May 31, 2007, dated December 12,
2003, from the Parent to Tail Wind, and (ii) Solomon, simultaneously with the
execution and delivery hereof, is purchasing from the Parent that certain 5%
Convertible Note Due May 31, 2007, dated December 12, 2003, from the Parent to
Solomon (such notes, together with any and all extensions, renewals and
modifications thereof, are collectively referred to herein as the "New Notes" );

         WHEREAS, the Mortgagor, simultaneously with the execution hereof, is
executing and delivering that certain Subsidiary Guaranty, dated as of December
12, 2003 (the "New Guaranty"), pursuant to which (inter alia) the Mortgagor is
guaranteeing the obligations and liabilities of the Parent under the New Notes,
the New Purchase Agreement, and that certain Registration Rights Agreement,
dated as of the date hereof, between the Parent and the Mortgagee (the "New
Registration Rights Agreement");

         WHEREAS, (i) the Mortgagor is receiving a substantial benefit from the
transactions contemplated by the New Purchase Agreement, and (ii) the Mortgagee
would not consummate such transactions without the execution and delivery by the
Mortgagor of the New Guaranty and this Amendment;

         WHEREAS, the Mortgagor and the Mortgagee desire for the Original
Mortgage, as amended by this Amendment, to secure (inter alia) (i) all of the
Mortgagor's obligations and liabilities under the New Guaranty and (ii) all of
the Parent's obligations and liabilities under the New Notes, the New Purchase
Agreement and the New Registration Rights Agreement; and

         WHEREAS, the parties have agreed to modify the terms and provisions of
the Original Mortgage (i) to allow the Original Mortgage (as amended hereby) to
secure such obligations and liabilities, and (ii) in certain other respects, all
as more particularly described below.

         NOW, THEREFORE, in consideration of TEN ($10.00) DOLLARS and other good
and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Mortgagor and the Mortgagee hereby agree as follows:

         1. Defined Terms. Unless otherwise specifically defined in this
Amendment, all capitalized terms used in this Amendment shall have the
respective meanings given to them in the Original Mortgage. The Original
Mortgage, as modified by this Amendment, is referred to herein as the
"Mortgage". From and after the date hereof, all references in the Original
Mortgage to "this Mortgage" (or words of similar import) shall mean the Original
Mortgage, as modified by this Amendment.


                                      -2-
<PAGE>

         2. Additional Security Covered by Original Mortgage. From and after the
date hereof, the Mortgage (i.e., the Original Mortgage as amended hereby) shall
secure, inter alia, (a) all of the Mortgagor's obligations and liabilities under
the New Guaranty, (b) all of the Mortgagor's obligations and liabilities under
the Mortgage, and (c) all of the Parent's obligations and liabilities under the
New Notes, the New Purchase Agreement and the New Registration Rights Agreement.
Accordingly, from and after the date hereof (and without limiting the generality
of the foregoing), (i) all references in the Original Mortgage to the "Notes"
shall include the New Notes; (ii) all references in the Original Mortgage to the
"Debt" or the "debt" shall include all of the principal, interest and other
amounts that are due and payable under the New Guaranty, the New Notes and/or
the Mortgage; (iii) all references in the Original Mortgage to the "Guaranty"
shall include the New Guaranty (as amended from time to time); (iv) all
references in the Original Mortgage to the "Purchase Agreement" shall include
the New Purchase Agreement (as amended from time to time); and (v) all
references in the Original Mortgage to the "Registration Rights Agreement" shall
include the New Registration Rights Agreement (as amended from time to time).

         3. Obligation to Maintain Liability Insurance; Indemnity for Third
Party Claims.

               (a) From and after the date hereof, the following two sentences
are added to Section 3 of the Original Mortgage, after the first sentence of
such Section 3: "The Mortgagor shall also maintain commercial general liability
insurance with respect to the Premises and the Improvements, on an "occurrence"
basis and in such amounts and containing such coverage as shall be reasonably
required by the Collateral Agent (so long as such amounts and coverage do not
exceed what is customarily required of owners of other comparable buildings in
the Mercer County, New Jersey area by institutional commercial lenders). The
Mortgagee shall be named as an additional insured on such commercial general
liability policy."

               (b) From and after the date hereof, clause (v) in the first
sentence of Section 43 of the Original Mortgage shall be deleted and replaced
with the following: "(v) any accident, injury to or death of persons or loss of
or damage to property occurring in, on or about the Mortgaged Property, and (vi)
any enforcement of this indemnification."

         4. Representations and Warranties. The Mortgagor represents and
warrants to the Mortgagee that all of the Mortgagor's representations and
warranties contained in Section 2, Section 7 and Section 9(b) of the Original
Mortgage are true and correct as of the date hereof, as if first made on the
date hereof (with the understanding that all references in such Sections to
"this Mortgage" or words of similar import shall mean the Original Mortgage, as
modified by this Amendment). In addition (and without limiting the generality of
the foregoing), the Mortgagor represents and warrants to the Mortgagee that:

               (a) Contemporaneously with, and in consideration for, the
execution and delivery of this Amendment, the Mortgagor is receiving new value
from the


                                      -3-
<PAGE>

Mortgagee, which new value is reasonably equivalent value in exchange for this
Amendment; and the execution and delivery of this Amendment by the Mortgagor
does not constitute a "fraudulent conveyance" within the meaning of Title 11 of
the United States Code as now constituted or under any other applicable statute.

               (b) The Mortgagor (i) has full power, authority and legal right
to execute and deliver this Amendment and to consummate the transactions
contemplated hereby, and (ii) has heretofore obtained all consents and approvals
(whether internal, third party or otherwise) required in connection with such
execution, delivery and consummation.

               (c) Upon recording of this Amendment, the Mortgagee will continue
to have a first priority lien on the real property and fixtures included within
the Mortgaged Property (notwithstanding the consummation of the transactions
contemplated by the New Purchase Agreement, including, without limitation, the
execution of this Amendment and the New Notes). In addition, without any
additional filings, the Mortgagee will continue to have a valid, perfected and
first priority security interest in the personal property included in the
Mortgaged Property (notwithstanding the consummation of the transactions
contemplated by the New Purchase Agreement, including, without limitation, the
execution of this Amendment and the New Notes).

               (d) No default exists under that certain Developer's Agreement,
dated September 1, 1999, between the Township of East Windsor and Simon
Developments, LLC, that encumbers the Premises; and no event has occurred which,
with the passage of time or the giving of notice or both, would constitute such
a default.

         5. New Jersey Provisions. The following Section 48 is hereby added to
the Original Mortgage:

               "48 New Jersey Provisions. This Mortgage is subject to
         modification as provided in N.J.S.A 46:9-8.1, and with respect to any
         such modification, the priority of this Mortgage shall relate back to
         and remain as it was at the time of recording of this Mortgage as if
         the modification was included herein or as if the modification occurred
         at the time of the recording of this Mortgage."

         6. Miscellaneous. (a) The Mortgagor acknowledges that, as of the date
hereof, Tail Wind is the Collateral Agent (as defined in and for purposes of the
Mortgage). Except as expressly modified hereby, the Original Mortgage remains
unmodified and in full force and effect. The Original Mortgage, as amended by
this Amendment, is hereby ratified and confirmed in all respects by the
Mortgagor. Without limiting the generality of the foregoing, the Mortgagor
represents and warrants to the Mortgagee that, as of the date hereof, (i) the
Mortgagor has no offsets, counterclaims or defenses to the enforcement of, or
otherwise with respect to, the Mortgage, and (ii) no Event of Default exists
under the Mortgage.


                                      -4-
<PAGE>

               (b) In the event of any conflict or inconsistency between the
terms, covenants and provisions of this Amendment and those of the Original
Mortgage, the terms, covenants and provisions of this Amendment shall control.

               (c) This Amendment may not be modified, amended, changed or
terminated except by an agreement in writing signed by the Mortgagor and the
Mortgagee.

               (d) This Amendment shall be binding upon and inure to the benefit
of the Mortgagor and the Mortgagee and their respective successors and assigns.

               (e) This Amendment may be executed in counterparts, each of which
shall be an original and all of which taken together shall constitute one and
the same instrument.

               (f) This Amendment shall be governed by and construed in
accordance with the laws of the State of New Jersey.


                     [REMAINDER OF PAGE INTENTIONALLY BLANK]













                                      -5-
<PAGE>

         IN WITNESS WHEREOF, the Mortgagee and the Mortgagor have caused this
Amendment to be duly executed as of the date first above written.


                                           MORTGAGOR:

                                           NEXMED (U.S.A.), INC.


                                           By: /s/ Vivian H. Liu
                                               ------------------
                                           Name:  Vivian H. Liu
                                           Title:  Vice President and Secretary


                                           MORTGAGEE:

                                           THE TAIL WIND FUND LTD.
                                           By:  TAIL WIND ADVISORY AND
                                           MANAGEMENT LTD., as
                                           investment manager


                                                By: /s/ Georgios Garafas
                                                    ---------------------
                                                Name:  Georgios Garafas
                                                Title:  Director


                                           SOLOMON STRATEGIC HOLDINGS, INC.


                                           By: /s/ Andrew P. MacKellar
                                               ------------------------
                                                Name: Andrew P. MacKellar
                                                Title: Director

                                           COLLATERAL AGENT:

                                           THE TAIL WIND FUND LTD.
                                           By:  TAIL WIND ADVISORY AND
                                           MANAGEMENT LTD., as
                                           investment manager


                                                By: /s/ Georgios Garafas
                                                    ---------------------
                                                Name:  Georgios Garafas
                                                Title:  Director




                                      -6-
<PAGE>

STATE OF                   )
        ---------------    )       ss.:
COUNTY OF                  )
         --------------

         On the ___ day of December in the year 2003 before me, the undersigned,
a Notary Public in and for said State, personally appeared ______________,
personally known to me or proved to me on the basis of satisfactory evidence to
be the individual whose name is subscribed to the within instrument and
acknowledged to me that he executed the same in his capacity/ies and that by his
signature(s) on the instrument, the individual, or the person(s) or entity/ies
upon behalf of which the individual acted, executed the instrument, and that
such individual made such appearance before the undersigned in
___________________________.

                                            -----------------------------
                                                     Notary Public

                           )
------------------------   )       ss.:
                           )
------------------------


         On the ___ day of November in the year 2003 before me, the undersigned,
personally appeared ______________, personally known to me or proved to me on
the basis of satisfactory evidence to be the individual whose name is subscribed
to the within instrument and acknowledged to me that he executed the same in his
capacity/ies and that by his signature(s) on the instrument, the individual, or
the person(s) or entity/ies upon behalf of which the individual acted, executed
the instrument, and that such individual made such appearance before the
undersigned in ______________________________.


                                            -----------------------------


                           )
------------------------   )       ss.:
                           )
------------------------

         On the ___ day of November in the year 2003 before me, the undersigned,
personally appeared ANDREW P. MACKELLAR, personally known to me or proved to me
on the basis of satisfactory evidence to be the individual whose name is
subscribed to the within instrument and acknowledged to me that he executed the
same in his capacity/ies and that by his signature(s) on the instrument, the
individual, or the person(s) or entity/ies upon behalf of which the individual
acted, executed the instrument, and that such individual made such appearance
before the undersigned in ______________________________.


                                            -----------------------------



                                      -7-
<PAGE>

                                    EXHIBIT A

                                Legal Description


All the real property located in the Township of East Windsor, County of Mercer,
State of New Jersey and more particularly described as follows:

BEGINNING at a point situated along the southerly right of way line of Twin
Rivers Drive (66 feet wide), said point being located 25.00 feet from the
intersection of the westerly prolongation of the same and the northerly
prolongation of the easterly right of way line of Milford Road (66 feet wide);
thence running

1.   South 85(degree) 22' 26" East along the southerly right of way line of Twin
     Rivers Drive, 208.27 feet to a point; thence

2.   Easterly along the same, along a curve to the right having a radius of
     967.00 feet and an arc length of 242.60 feet to a point; thence

3.   South 06(degree) 55' 34" West along the common line of Lots 6 and 190 Block
     20.06, 371.02 feet to a point; thence

4.   North 80(degree) 46' 41" West along the common line of Lots 4 and 6 Block
     20.06, 293.02 feet to a point; thence

5.   North 04(degree) 37' 34" East along the common line of Lots 5 and 6 Block
     20.06, 150.00 feet to a point; thence

6.   North 80(degree) 46' 41" West along the same, 166.90 feet to a point;
     thence

7.   North 04(degree) 37' 34" East along the easterly line of Milford Road,
     189.14 feet to a point; thence

8.   Easterly along the same, along a curve to the right having a radius of
     25.00 feet and an arc length of 39.27 feet to the point and place of
     beginning.


NOTE:     BEING Lot 6, Block 20.06, Tax Map of the Township of East Windsor,
          Mercer County, New Jersey,

          BEING commonly known as 89 Twin Rivers Drive, East Windsor, New Jersey
          08520,


                                      -8-
<PAGE>

          BEING the same premises conveyed to the Mortgagor herein by deed dated
          October 17, 2000 and recorded on November 1, 2000 in the Mercer County
          Register's Office in Deed Book 3937, page 254.






















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