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): September 9, 2011

VIROPHARMA INCORPORATED

(Exact Name of Registrant as Specified in its Charter)

(610) 458-7300

(Registrant’s Telephone Number, Including Area Code)

Check the appropriate box below if the Form 8-K is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

On September 9, 2011, ViroPharma Incorporated (the “Company”) entered into a $200 million, three-year senior secured revolving credit facility (the “Credit Facility”), the terms of which are set forth in a Credit Agreement dated as of September 9, 2011 (the “Credit Agreement”) among the Company, the lenders named therein, JPMorgan Chase Bank, N.A., as administrative agent (the “Administrative Agent”), and BMO Harris Financing Inc., TD Bank, N.A. and Morgan Stanley Bank, NA as co-syndication agents.

The Credit Facility will be available for working capital and general corporate purposes, including acquisitions which comply with the terms of the Credit Agreement. The Credit Agreement provides separate sub-limits for letters of credit up to $20 million and swing line loans up to $10 million.

The Credit Agreement requires the Company to maintain (i) a maximum senior secured leverage ratio of less than 2.00 to 1.00, (ii) a maximum total leverage ratio of less than 3.50 to 1.00, (iii) a minimum interest coverage ratio of greater than 3.50 to 1.00 and (iv) minimum liquidity equal to or greater than the sum of $100,000,000 plus the aggregate amount of certain contingent consideration resulting from business acquisitions payments payable by the Company within a specified time period. The Credit Agreement contains additional affirmative and negative covenants that the Company believes are usual and customary for a senior secured credit agreement. The negative covenants include, among other things, limitations on capital expenditures, asset sales, mergers and acquisitions, indebtedness, liens, dividends, investments and transactions with the Company’s affiliates.

The obligations of the Company under the Credit Facility are guaranteed by certain of the Company’s domestic subsidiaries (the “Subsidiary Guarantors”) and are secured by substantially all of the assets of the Company and the Subsidiary Guarantors, including but not limited to: (a) pledges of and first priority perfected security interests in 100% of the equity interests of certain of the Company’s and the Subsidiary Guarantors’ domestic subsidiaries and 65% of the equity interests of a foreign subsidiary of certain Subsidiary Guarantors and (b) perfected first priority security interests in substantially all other tangible and intangible assets of the Company and each Subsidiary Guarantor, subject to certain exceptions.

Borrowings under the Credit Facility will bear interest at an amount equal to a rate calculated based on the type of borrowing and the Company’s Senior Secured Leverage Ratio (as defined in the Credit Agreement) from time to time. For example, for loans (other than swing line loans), the Company may elect to pay interest based on adjusted LIBOR plus between 2.25% and 2.75% or an Alternate Base Rate (as defined in the Credit Agreement) plus between 1.25% and 1.75%. The Company will also pay a commitment fee of between 35 to 45 basis points, payable quarterly, on the average daily unused amount of the Revolving Credit Facility based on the Company’s Senior Secured Leverage Ratio from time to time.

During the continuance of an event of default, amounts owing under the Credit Facility will bear interest at a rate per annum equal to the rate otherwise applicable thereto plus an additional 2.0%.

As of the date of this filing, the Company has not drawn any amounts under the Credit Facility.

The Company intends to file a copy of the Credit Agreement as an exhibit to the Company’s quarterly report on Form 10-Q for the third quarter of 2011.

The information required by Item 2.03 is contained in Item 1.01 above and is incorporated herein by reference.

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.