Exhibit (a)(1)(D)

Offer to Purchase for Cash

All Outstanding Shares of Common Stock

(Including the Associated Preferred Stock Purchase Rights)

of

INSPIRE PHARMACEUTICALS, INC.

at

$5.00 Net Per Share

by

MONARCH TRANSACTION CORP.

a wholly-owned subsidiary of

MERCK & CO., INC.

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON THURSDAY, MAY 12, 2011, UNLESS THE OFFER IS EXTENDED.

To Brokers, Dealers, Banks, Trust Companies and other Nominees: April 15, 2011

Monarch Transaction Corp., a Delaware corporation (the “Purchaser”) and a wholly-owned subsidiary of Merck & Co., Inc., a company formed under the laws of New Jersey (“Merck”), is making an offer to purchase all outstanding shares of common stock, par value $0.001 per share (including the associated preferred stock purchase rights, each a “Share” and collectively, the “Shares”), of Inspire Pharmaceuticals, Inc., a Delaware corporation (“Inspire”), at $5.00 per share, net to the seller in cash, without interest, upon the terms and subject to the conditions set forth in the Offer to Purchase dated April 15, 2011 (the “Offer to Purchase”) and in the related Letter of Transmittal (which, together with any amendments or supplements thereto, collectively constitute the “Offer”).

Please furnish copies of the enclosed materials to those of your clients for whom you hold Shares registered in your name or in the name of your nominee.

Enclosed herewith are copies of the following documents:

1. Offer to Purchase dated April 15, 2011;

2. Letter of Transmittal to be used by shareholders of Inspire in accepting the Offer;

3. The Letter to Shareholders of Inspire from the President and Chief Executive Officer of Inspire accompanied by Inspire’s Solicitation/Recommendation Statement on Schedule 14D-9;

4. A printed form of letter that may be sent to your clients for whose account you hold Shares in your name or in the name of a nominee, with space provided for obtaining the clients’ instructions with regard to the Offer; and

5. Notice of Guaranteed Delivery with respect to the Shares.

We request that you contact your clients promptly. Please note that the Offer and any withdrawal rights will expire at 12:00 midnight, New York City time, on Thursday, May 12, 2011, unless extended.

Neither the Purchaser nor Merck will pay any fees or commissions to any broker or dealer or other person (other than the Depositary and the Information Agent, as described in the Offer to Purchase) in connection with the solicitation of tenders of Shares in the Offer. You will be reimbursed by the Purchaser upon request for customary mailing and handling expenses incurred by you in forwarding the enclosed materials to your customers.

Questions and requests for additional copies of the enclosed materials may be directed to Georgeson Inc., the Information Agent, at the address appearing on the back page of the Offer to Purchase.

Very truly yours,

Merck & Co., Inc.

NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL RENDER YOU OR ANY OTHER PERSON THE AGENT OF THE PURCHASER, MERCK, THE DEPOSITARY OR THE INFORMATION AGENT OR AUTHORIZE YOU OR ANY OTHER PERSON TO GIVE ANY INFORMATION OR MAKE ANY REPRESENTATION ON BEHALF OF ANY OF THEM WITH RESPECT TO THE OFFER NOT CONTAINED IN THE OFFER TO PURCHASE OR THE LETTER OF TRANSMITTAL.