SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C.  20549

SCHEDULE 13D

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO

RULE 13d-2(a)

(Amendment No. 4)*

CPEX Pharmaceuticals, Inc.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

12620N104

(CUSIP Number)

The Mangrove Partners Fund, L.P.

10 East 53rd Street, 31st Floor

New York, New York 10022

Attention: Nathaniel August

Tel:  646.450.0418

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

Copies to:

John T. O’Connor

Sadis & Goldberg LLP

551 Fifth Avenue, 21st Floor

New York, New York 10176

Tel: 212.573.8029

March 16, 2011

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box  o.

Note.  Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7(b) for other parties to whom copies are to be sent.

* 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 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 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.)

CUSIP No.:  12620N104

NAME OF REPORTING PERSON
1.	S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
	The Mangrove Partners Fund, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a) x
	(b) ¨
3	SEC USE ONLY
4	SOURCE OF FUNDS
	WC, OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) or 2(e)  ¨
6.	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware

NUMBER OF	7	SOLE VOTING POWER   -   0
SHARES
BENEFICIALLY	8	SHARED VOTING POWER   -   149,373
OWNED BY
EACH	9	SOLE DISPOSITIVE POWER   -     0
REPORTING
PERSON WITH	10	SHARED DISPOSITIVE POWER   - 149,373

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	149,373
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES  ¨
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	5.7%*
14	TYPE OF REPORTING PERSON
	PN

*  The ownership percentage is calculated based on 2,616,936 shares of Common Stock outstanding as of January 31, 2011, as reported in the Issuer’s Definitive Proxy Statement on Schedule 14A, as filed with the Securities and Exchange Commission on February 4, 2011.

Page 2 of 7 pages

 

CUSIP No.:  12620N104

1	NAME OF REPORTING PERSON
	S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
	Mangrove Partners
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a) x
	(b) ¨
3	SEC USE ONLY
4	SOURCE OF FUNDS
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) or 2(e)  ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Cayman Islands

NUMBER OF	7	SOLE VOTING POWER   -   0
SHARES
BENEFICIALLY	8	SHARED VOTING POWER   -   149,373
OWNED BY
EACH	9	SOLE DISPOSITIVE POWER   -   0
REPORTING
PERSON WITH	10	SHARED DISPOSITIVE POWER   -   149,373

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	149,373
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES ¨
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	5.7%*
14	TYPE OF REPORTING PERSON
	OO

*  The ownership percentage is calculated based on 2,616,936 shares of Common Stock outstanding as of January 31, 2011, as reported in the Issuer’s Definitive Proxy Statement on Schedule 14A, as filed with the Securities and Exchange Commission on February 4, 2011.

Page 3 of 7 pages

 

CUSIP No.:  12620N104

1	NAME OF REPORTING PERSON
	S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
	Mangrove Capital
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a) x
	(b) ¨
3	SEC USE ONLY
4	SOURCE OF FUNDS
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) or 2(e)  ¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Cayman Islands

NUMBER OF	7	SOLE VOTING POWER   -   0
SHARES
BENEFICIALLY	8	SHARED VOTING POWER   -   149,373
OWNED BY
EACH	9	SOLE DISPOSITIVE POWER   -   0
REPORTING
PERSON WITH	10	SHARED DISPOSITIVE POWER   -  149,373

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	149,373
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	5.7%*
14	TYPE OF REPORTING PERSON
	OO

*  The ownership percentage is calculated based on 2,616,936 shares of Common Stock outstanding as of January 31, 2011, as reported in the Issuer’s Definitive Proxy Statement on Schedule 14A, as filed with the Securities and Exchange Commission on February 4, 2011.

Page 4 of 7 pages

 

Explanatory Note

This Amendment No. 4 to Schedule 13D (this “Amendment No. 4”) is being filed with respect to the beneficial ownership of common stock, par value $0.01 per share (the “Common Stock”), of CPEX Pharmaceuticals, Inc., a Delaware corporation (the “Issuer” or the “Company”).  This Amendment No. 4 supplements Items 4 and 7 of the Schedule 13D (as amended) originally filed on January 31, 2011.

ITEM 4. Purpose of Transaction.

On March 16, 2011, Mangrove Partners delivered a letter to the board of directors of the Issuer (the “Board”) setting forth revised indicative terms of a fully-financed dividend recapitalization of the Issuer to be implemented through a backstopped rights issue (“Revised Recapitalization Letter”).  The Revised Recapitalization Letter updated the Board with respect to the identity and number of the backstop participants in the proposed dividend recapitalization and supersedes the letter previously sent by Mangrove Partners to the Board on March 14, 2011 (and attached as Exhibit 99.1 to Amendment No. 3 to Schedule 13D, filed with the SEC on March 14, 2011).  A copy of the Revised Recapitalization Letter from Mangrove Partners is attached hereto as Exhibit 99.1 and is incorporated herein by reference. The description herein of the Revised Recapitalization Letter is qualified in its entirety by reference to the Revised Recapitalization Letter.

All of the shares of Common Stock reported herein as being beneficially owned by the Reporting Persons were acquired for investment purposes.  Except as set forth herein or as would occur upon completion of any of the actions discussed herein, including in any Exhibits hereto, the Reporting Persons have no present plan or proposal that would relate to or result in any of the matters set forth in subparagraphs (a)-(j) of Item 4 of Schedule 13D.  The Reporting Persons intend to review its investment in the Issuer on a continuing basis and depending on various factors including, without limitation, the Issuer's financial position and strategic direction, the outcome of the discussions and actions referenced above, actions taken by the Board, price levels of the Common Stock, other investment opportunities available to the Reporting Persons, conditions in the securities market and general economic and industry conditions, the Reporting Persons may in the future take such actions with respect to its investment in the Issuer as it deems appropriate including, without limitation, purchasing additional shares of Common Stock or selling some or all of its Common Stock, engaging in short selling of or any hedging or similar transactions with respect to the Common Stock and/or otherwise changing its intention with respect to any and all matters referred in Item 4 of Schedule 13D; provided that the Reporting Persons expressly disclaim any intention of engaging in a control transaction or a contested election of directors of the Issuer’s Board.

ITEM 7. Material to be Filed as Exhibits.

Exhibit No.	Document
99.1	Letter to CPEX Pharmaceuticals, Inc., dated March 16, 2011

Page 5 of 7 pages

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:  March 16, 2011

THE MANGROVE PARTNERS FUND, L.P.
MANGROVE PARTNERS
MANGROVE CAPITAL
By:	/s/ Nathaniel August
Nathaniel August, for himself, as Director of Mangrove Capital (for itself and The Mangrove Partners Fund, L.P.) and as a Director of Mangrove Partners

Page 6 of 7 pages

EXHIBIT INDEX

Exhibit No.	Document
99.1	Letter to CPEX Pharmaceuticals, Inc., dated March 16, 2011

Page 7 of 7 pages