UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934
                               (Amendment No. 1)*

                         UNITED THERAPEUTICS CORPORATION
--------------------------------------------------------------------------------
                                (Name of Issuer)

                     Common Stock, $0.01 Par Value Per Share
--------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    91307C102
                                    ---------
                                 (CUSIP Number)

                                December 31, 2006
                                -----------------
                      (Date of Event which Requires Filing
                               of this Statement)



Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

            [ ]    Rule 13d-1(b)
            [X]    Rule 13d-1(c)
            [ ]    Rule 13d-1(d)



*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).


                                  Page 1 of 11





-------------------                                           ------------------
CUSIP No. 91307C102                   13G                     Page 2 of 11 Pages
-------------------                                           ------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           S.A.C. Capital Advisors, LLC
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                      (a) [ ]
                                                                      (b) [X]
---------- ---------------------------------------------------------------------
        3  SEC USE ONLY

---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           Delaware
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
NUMBER OF             ----- ----------------------------------------------------
SHARES                   6  SHARED VOTING POWER
BENEFICIALLY
OWNED                       74,299 (see Item 4)
BY                    ----- ----------------------------------------------------
EACH                     7  SOLE DISPOSITIVE POWER
REPORTING
PERSON                      0
WITH                  ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            74,299 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           74,299 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]
---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           0.3% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           00
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT


                                  Page 2 of 11





-------------------                                           ------------------
CUSIP No. 91307C102                   13G                     Page 3 of 11 Pages
-------------------                                           ------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           S.A.C. Capital Management, LLC
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                      (a) [ ]
                                                                      (b) [X]
---------- ---------------------------------------------------------------------
        3  SEC USE ONLY

---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           Delaware
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
NUMBER OF             ----- ----------------------------------------------------
SHARES                   6  SHARED VOTING POWER
BENEFICIALLY
OWNED                       74,299 (see Item 4)
BY                    ----- ----------------------------------------------------
EACH                     7  SOLE DISPOSITIVE POWER
REPORTING
PERSON                      0
WITH                  ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            74,299 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           74,299 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]
---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           0.3% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           00
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT


                                  Page 3 of 11





-------------------                                           ------------------
CUSIP No. 91307C102                   13G                     Page 4 of 11 Pages
-------------------                                           ------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           CR Intrinsic Investors, LLC
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                      (a) [ ]
                                                                      (b) [X]
---------- ---------------------------------------------------------------------
        3  SEC USE ONLY

---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           Delaware
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
NUMBER OF             ----- ----------------------------------------------------
SHARES                   6  SHARED VOTING POWER
BENEFICIALLY
OWNED                       0 (see Item 4)
BY                    ----- ----------------------------------------------------
EACH                     7  SOLE DISPOSITIVE POWER
REPORTING
PERSON                      0
WITH                  ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            0 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           0 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]
---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           0% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           00
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT


                                  Page 4 of 11





-------------------                                           ------------------
CUSIP No. 91307C102                   13G                     Page 5 of 11 Pages
-------------------                                           ------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           Sigma Capital Management, LLC
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                      (a) [ ]
                                                                      (b) [X]
---------- ---------------------------------------------------------------------
        3  SEC USE ONLY

---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           Delaware
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
NUMBER OF             ----- ----------------------------------------------------
SHARES                   6  SHARED VOTING POWER
BENEFICIALLY
OWNED                       65,000 (see Item 4)
BY                    ----- ----------------------------------------------------
EACH                     7  SOLE DISPOSITIVE POWER
REPORTING
PERSON                      0
WITH                  ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            65,000 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           65,000 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]
---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           0.3% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           00
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT


                                  Page 5 of 11





-------------------                                           ------------------
CUSIP No. 91307C102                   13G                     Page 6 of 11 Pages
-------------------                                           ------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           Steven A. Cohen
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                      (a) [ ]
                                                                      (b) [X]
---------- ---------------------------------------------------------------------
        3  SEC USE ONLY

---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           United States
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
NUMBER OF             ----- ----------------------------------------------------
SHARES                   6  SHARED VOTING POWER
BENEFICIALLY
OWNED                       139,299 (see Item 4)
BY                    ----- ----------------------------------------------------
EACH                     7  SOLE DISPOSITIVE POWER
REPORTING
PERSON                      0
WITH                  ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            139,299 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           139,299 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]
---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           0.6% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           IN
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT


                                  Page 6 of 11





Item 1(a)           Name of Issuer:
                    --------------

                    United Therapeutics Corporation

Item 1(b)           Address of Issuer's Principal Executive Offices:
                    -----------------------------------------------

                    1110 Spring Street
                    Silver Spring, MD  20910

Items 2(a)          Name of Person Filing:
                    ---------------------

                    This statement is filed by: (i) S.A.C. Capital Advisors,
                    LLC, ("SAC Capital Advisors") with respect to shares of
                    common stock, par value $0.01 per share ("Shares"), of the
                    Issuer beneficially owned by S.A.C. Capital Associates, LLC
                    ("SAC Capital Associates") and S.A.C. MultiQuant Fund, LLC
                    ("SAC MultiQuant"); (ii) S.A.C. Capital Management, LLC,
                    ("SAC Capital Management") with respect to Shares
                    beneficially owned by SAC Capital Associates and SAC
                    MultiQuant; (iii) CR Intrinsic Investors, LLC ("CR Intrinsic
                    Investors") with respect to Shares beneficially owned by CR
                    Intrinsic Investments, LLC ("CR Intrinsic Investments");
                    (iv) Sigma Capital Management, LLC ("Sigma Management") with
                    respect to Shares beneficially owned by Sigma Capital
                    Associates, LLC ("Sigma Capital Associates") and (v) Steven
                    A. Cohen with respect to Shares beneficially owned by SAC
                    Capital Advisors, SAC Capital Management, SAC Capital
                    Associates, SAC MultiQuant, CR Intrinsic Investors, CR
                    Intrinsic Investments, Sigma Management and Sigma Capital
                    Associates.

                    SAC Capital Advisors, SAC Capital Management, CR Intrinsic
                    Investors, Sigma Management and Steven A. Cohen have entered
                    into a Joint Filing Agreement, a copy of which is filed with
                    this Schedule 13G as Exhibit 99.1, pursuant to which they
                    have agreed to file this Schedule 13G jointly in accordance
                    with the provisions of Rule 13d-1(k) of the Securities
                    Exchange Act of 1934, as amended.

Item 2(b)           Address of Principal Business Office:
                    ------------------------------------

                    The address of the principal business office of (i) SAC
                    Capital Advisors, CR Intrinsic Investors and Mr. Cohen is 72
                    Cummings Point Road, Stamford, Connecticut 06902 and (ii)
                    SAC Capital Management and Sigma Management is 540 Madison
                    Avenue, New York, New York 10022.


                                  Page 7 of 11





Item 2(c)           Citizenship:
                    -----------

                    SAC Capital Advisors, SAC Capital Management, CR Intrinsic
                    Investors and Sigma Management are Delaware limited
                    liability companies. Mr. Cohen is a United States citizen.

Item 2(d)           Title of Class of Securities:
                    ----------------------------

                    Common Stock, par value $0.01 per share

Item 2(e)           CUSIP Number:
                    ------------

                    91307C102

Item 3              Not Applicable

Item 4              Ownership:
                    ---------

                    The percentages used herein are calculated based upon the
                    Shares issued and outstanding as of October 27, 2006 as
                    reported on the Issuer's quarterly report on Form 10-Q filed
                    with the Securities and Exchange Commission by the Issuer
                    for the quarterly period ended September 30, 2006.

                    As of the close of business on December 31, 2006:

                    1. S.A.C. Capital Advisors, LLC
                    (a) Amount beneficially owned: 74,299
                    (b) Percent of class: 0.3%
                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii) Shared power to vote or direct the vote: 74,299
                    (iii) Sole power to dispose or direct the disposition: -0-
                    (iv) Shared power to dispose or direct the disposition:
                    74,299

                    2. S.A.C. Capital Management, LLC
                    (a) Amount beneficially owned: 74,299
                    (b) Percent of class: 0.3%
                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii) Shared power to vote or direct the vote: 74,299
                    (iii) Sole power to dispose or direct the disposition: -0-
                    (iv) Shared power to dispose or direct the disposition:
                    74,299

                    3. CR Intrinsic Investors, LLC
                    (a) Amount beneficially owned: -0-
                    (b) Percent of class: 0%


                                  Page 8 of 11





                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii) Shared power to vote or direct the vote: -0-
                    (iii) Sole power to dispose or direct the disposition: -0-
                    (iv) Shared power to dispose or direct the disposition: -0-

                    4. Sigma Capital Management, LLC
                    (a) Amount beneficially owned: 65,000
                    (b) Percent of class: 0.3%
                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii) Shared power to vote or direct the vote: 65,000
                    (iii) Sole power to dispose or direct the disposition: -0-
                    (iv) Shared power to dispose or direct the disposition:
                    65,000

                    5. Steven A. Cohen
                    (a) Amount beneficially owned: 139,299
                    (b) Percent of class: 0.6%
                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii) Shared power to vote or direct the vote: 139,299
                    (iii) Sole power to dispose or direct the disposition: -0-
                    (iv) Shared power to dispose or direct the disposition:
                    139,299

                    SAC Capital Advisors, SAC Capital Management, CR Intrinsic
                    Investors, Sigma Management and Mr. Cohen own directly no
                    Shares. Pursuant to investment agreements, each of SAC
                    Capital Advisors and SAC Capital Management share all
                    investment and voting power with respect to the securities
                    held by SAC Capital Associates and SAC MultiQuant. Pursuant
                    to an investment management agreement, CR Intrinsic
                    Investors maintains investment and voting power with respect
                    to the securities held by CR Intrinsic Investments. Pursuant
                    to an investment management agreement, Sigma Management
                    maintains investment and voting power with respect to the
                    securities held by Sigma Capital Associates. Mr. Cohen
                    controls each of SAC Capital Advisors, SAC Capital
                    Management, CR Intrinsic Investors and Sigma Management. CR
                    Intrinsic Investments is a wholly owned subsidiary of SAC
                    Capital Associates. By reason of the provisions of Rule
                    13d-3 of the Securities Exchange Act of 1934, as amended,
                    each of (i) SAC Capital Advisors, SAC Capital Management and
                    Mr. Cohen may be deemed to own beneficially 74,299 Shares
                    (constituting approximately 0.3% of the Shares outstanding)
                    and (ii) Sigma Management and Mr. Cohen may be deemed to own
                    beneficially 65,000 shares (constituting approximately 0.3%
                    of the Shares outstanding). Each of SAC Capital Advisors,
                    SAC Capital Management, CR Intrinsic Investors, Sigma
                    Management and Mr. Cohen disclaim beneficial ownership of
                    any of the securities covered by this statement.


                                  Page 9 of 11





Item 5              Ownership of Five Percent or Less of a Class:
                    --------------------------------------------

                    If this statement is being filed to report the fact that as
                    of the date hereof the reporting person has ceased to be the
                    beneficial owner of more than five percent of the class of
                    securities, check the following. [X]

Item 6              Ownership of More than Five Percent on Behalf of Another
                    --------------------------------------------------------
                    Person:
                    ------

                    Not Applicable

Item 7              Identification and Classification of the
                    ----------------------------------------
                    Subsidiary Which Acquired the Security Being
                    --------------------------------------------
                    Reported on By the Parent Holding Company:
                    -----------------------------------------

                    Not Applicable

Item 8              Identification and Classification of Members
                    --------------------------------------------
                    of the Group:
                    ------------

                    Not Applicable

Item 9              Notice of Dissolution of Group:
                    ------------------------------

                    Not Applicable

Item 10             Certification:
                    -------------

     By signing below the signatory certifies that, to the best of his knowledge
and belief, the securities referred to above were not acquired and are not held
for the purpose of or with the effect of changing or influencing the control of
the issuer of the securities and were not acquired and are not held in
connection with or as a participant in any transaction having that purpose or
effect.


                                 Page 10 of 11





                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Dated: February 14, 2007

S.A.C. CAPITAL ADVISORS, LLC


By: /s/ Peter Nussbaum
   ---------------------------
Name:   Peter Nussbaum
Title:  Authorized Person


S.A.C. CAPITAL MANAGEMENT, LLC


By: /s/ Peter Nussbaum
   ---------------------------
Name:   Peter Nussbaum
Title:  Authorized Person


CR INTRINSIC INVESTORS, LLC


By: /s/ Peter Nussbaum
   ---------------------------
Name:   Peter Nussbaum
Title:  Authorized Person


SIGMA CAPITAL MANAGEMENT, LLC


By: /s/ Peter Nussbaum
   ---------------------------
Name:   Peter Nussbaum
Title:  Authorized Person


STEVEN A. COHEN


By: /s/ Peter Nussbaum
   ---------------------------
Name:   Peter Nussbaum
Title:  Authorized Person


                                 Page 11 of 11