UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 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): January 12, 2015

ZOGENIX, INC.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (858) 259-1165

(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):

On January 12, 2015, Zogenix, Inc. (the “Company” or “Zogenix”) announced that its preliminary unaudited cash and cash equivalents as of December 31, 2014 were approximately $42.2 million, including $21.5 million in cash from a term loan and a revolving line of credit with Oxford Finance LLC and Silicon Valley Bank. In addition, $8.5 million is being held in escrow from the proceeds of the sale of Sumavel DosePro to Endo Pharmaceuticals.

The preliminary unaudited cash position discussed above is subject to the completion of financial closing procedures and other developments that may arise between now and the time the financial results for the fourth quarter are finalized, as well as the completion of the audit of the 2014 financial statements. Therefore, actual results may differ materially from these estimates. In addition, the above estimates do not present all information necessary for an understanding of Zogenix’s financial condition as of December 31, 2014.

In accordance with General Instruction B.2 of Form 8-K, the information in this Current Report on Form 8-K shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liability of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, whether made before or after the date hereof, except as expressly set forth by specific reference in such filing to this Current Report on Form 8-K.

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Zogenix cautions you that statements included in this report that are not a description of historical facts are forward-looking statements. Words such as “believes,” “anticipates,” “plans,” “expects,” “indicates,” “will,” “intends,” “potential,” “suggests,” “assuming” and similar expressions are intended to identify forward-looking statements. These statements are based on the Company’s current beliefs and expectations. These forward-looking statements include statements regarding Zogenix’s cash position as of December 31, 2014. The inclusion of forward-looking statements should not be regarded as a representation by Zogenix that any of its plans will be achieved. Actual results may differ from those set forth in this report due to the risks and uncertainties inherent in Zogenix’s business, including, without limitation: risks related to changes in estimated financial amounts based on the completion of financial closing procedures and the audit of the financial statements; and other risks described in Zogenix’s filings with the Securities and Exchange Commission. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and Zogenix undertakes no obligation to revise or update this report to reflect events or circumstances after the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement. This caution is made under the safe harbor provisions of Section 21E of the Private Securities Litigation Reform Act of 1995.

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.