UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): April 12, 2012

PACIRA PHARMACEUTICALS, INC.

(Exact Name of Registrant as Specified in Charter)

Registrant’s telephone number, including area code: (973) 254-3560

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

o            Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o            Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o            Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o            Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 1.01 Entry into a Material Definitive Agreement.

On April 12, 2012, Pacira Pharmaceuticals, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with the several Underwriters named in the Underwriting Agreement (the “Underwriters”) for which Jefferies & Company, Inc. and Barclays Capital Inc. are acting as representatives, relating to an underwritten public offering of 6,000,000 shares (the “Shares”) of the Company’s common stock, par value $0.001 per share (the “Common Stock”). All of the shares are being sold by the Company. The offering price to the public is $9.75 per share, and the Underwriters have agreed to purchase the Shares from the Company pursuant to the Underwriting Agreement at a price of $9.165 per share. After underwriting discounts and commissions and estimated offering expenses, the Company expects to receive net proceeds of approximately $54.6 million. Under the terms of the Underwriting Agreement, the Company has granted the Underwriters an option, exercisable for 30 days, to purchase up to an additional 900,000 shares of Common Stock to cover over-allotments, if any, at the same price.

The Shares will be issued pursuant to a shelf registration statement the Company filed with the Securities and Exchange Commission, which became effective on April 5, 2012 (File No. 333-180384). A prospectus supplement relating to the offering has been filed with the Securities and Exchange Commission. The closing of the offering is expected to take place on April 17, 2012, subject to the satisfaction of customary closing conditions.

The Underwriting Agreement is filed as Exhibit 1.1 to this Current Report on Form 8-K, and such document is incorporated herein by reference. The foregoing is only a brief description of the material terms of the Underwriting Agreement, does not purport to be a complete description of the rights and obligations of the parties thereunder and is qualified in its entirety by reference to such exhibit.

The legal opinion and consent of Wilmer Cutler Pickering Hale and Dorr LLP relating to the Shares is filed as Exhibit 5.1 to this Current Report on Form 8-K, and such document is incorporated herein by reference.

Item 8.01. Other Events.

The Company issued a press release on April 12, 2012 announcing the pricing of the Shares described in Item 1.01 above. The full text of the press release issued in connection with this announcement is filed as Exhibit 99.1 to this Current Report on Form 8-K, and the information contained therein is incorporated herein by reference.

Neither the filing of the press release as an exhibit to this Current Report on Form 8-K nor the inclusion in the press release of a reference to the Company’s internet address shall, under any circumstances, be deemed to incorporate the information available at its internet address into this Current Report on Form 8-K. The information available at the Company’s internet address is not part of this Current Report on Form 8-K or any other report filed by the Company with the Securities and Exchange Commission.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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EXHIBIT INDEX

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