Subject: Partial Termination of Convertible Bond Hedge Transaction Reference No. 50302802 Date: March 19, 2009 This letter agreement (this "Termination Agreement") relates to the Transaction (the "Transaction") entered into between Credit Suisse International ("Dealer"), represented by

To:

ViroPharma Incorporated

730 Stockton Drive

Exton, PA 19341

A/C

YMJTD0

From:

Credit Suisse International

One Cabot Square

London E14 4QJ

England

Subject:

Partial Termination of Convertible Bond Hedge Transaction Reference No. 50302802

Date:

March 19, 2009

Termination Payment Amount:

For each Payment Date, an amount in USD equal to the product of the Applicable Number of Options for such Payment Date and the Termination Value for such Payment Date, as set forth in the Calculation Agent’s Notice for the related Purchase Date.

Applicable Number of Options:

For each Payment Date, the Number of Purchased Convertible Notes for such Payment Date, as set forth in the Calculation Agent’s Notice for the related Purchase Date.

Number of Purchased Convertible Notes:

For each Payment Date, the number of Convertible Notes (in denominations of USD1,000 principal amount) purchased by Counterparty on the Purchase Date corresponding to such Payment Date pursuant to the Purchase Program, as set forth in the Calculation Agent’s Notice for the related Purchase Date.

Purchase Date:

Each date on which Counterparty executes a purchase of Convertible Notes pursuant to the Purchase Program. For the

avoidance of doubt, the Purchase Date shall be the trade date of such purchase.

Termination Value:

For each Payment Date the amount, as determined by the Calculation Agent, that would be payable by Dealer to Counterparty pursuant to Section 6 of the Agreement if (i) Dealer designated an Early Termination Date in respect of an Additional Termination Event, with Counterparty as the sole Affected Party and the Transaction as the sole Affected Transaction, occurring on the Purchase Date corresponding to such Payment Date and (ii) the Number of Options for the Transaction were one. For purposes of determining such amount, the Calculation Agent shall (i) use the Average VWAP Price corresponding to such Purchase Date as the current Share price input and (ii) assume that all Convertible Notes originally issued by Counterparty remain outstanding on the Early Termination Date.

Calculation Agent’s Notice:

A notice for each Purchase Date to be provided by the Calculation Agent to Counterparty following the close of trading on the Exchange on the Final Averaging Date for such Purchase Date substantially in the form attached hereto as Schedule A. For the avoidance of doubt, the Number of Purchased Convertible Notes set forth in the Calculation Agent’s Notice shall be identical to the number of Convertible Notes repurchased by Counterparty indicated in the Notice of Purchased Convertible Notes for such Purchase Date.

Notice of Number of Purchased Convertible Notes:

Counterparty may notify Dealer in writing (including by email) before 7:00 PM (New York City time) on each Purchase Date of the number of Convertible Notes purchased by Counterparty on such Purchase Date. If Counterparty so notifies Dealer, such Convertible Notes purchased by Counterparty shall be subject to the provisions hereunder.

Averaging Dates:

For each Purchase Date, the immediately following Exchange Business Day.

Average VWAP Price:

For each Purchase Date, the arithmetic average of the Daily Average Price on each of the Averaging Dates corresponding to such Purchase Date.

Daily Average Price:

For any Exchange Business Day, as determined by the Calculation Agent based on the New York Volume Weighted Average Price per Share for the regular trading session (including any extensions thereof) of the Exchange on such Exchange Business Day (without regard to pre-open or after hours trading outside of such regular trading session), as published by Bloomberg at 4:15 P.M., New York City time (or 15 minutes following the end of any extension of the regular trading session), on such Exchange Business Day, on Bloomberg page “VPHM.Q<Equity>AQR” (or any successor thereto) (or if such published volume weighted average price is unavailable or is manifestly incorrect, the market value of one Share on such Exchange Business Day, as determined by the Calculation Agent using a volume weighted method).

Exchange:

The NASDAQ Global Select Market

Consequences of Disrupted Days:

Notwithstanding anything to the contrary in this Termination Agreement or the Equity Definitions, if any Averaging Date is a Disrupted Day, the Calculation Agent may, if appropriate in light of market conditions, regulatory considerations or otherwise, take any or all of the following actions: (i) postpone such Averaging Date in accordance with Section 6.7 of the Equity Definitions as if “Modified Postponement” were applicable or (ii) determine that such Averaging Date is a Disrupted Day only in part, in which case the Calculation Agent shall (A) determine the Daily Average Price for such Averaging Date based on transactions in the Shares on such Averaging Date effected before the relevant Market Disruption Event occurred and/or after the relevant Market Disruption Event ended, as applicable, and (B) designate the immediately following Exchange Business Day that is not already an Averaging Date as an Averaging Date (with the provisions of this paragraph applying successively to each such Exchange Business Day so designated) and determine the Termination Value using an appropriately weighted average of the Daily Average Prices on the Averaging Dates. Section 6.7(c)(iii)(A) of the Equity Definitions is hereby amended by replacing the word “shall” in the sixth line thereof with the word “may,” and by deleting