SAN DIEGO — Somaxon Pharmaceuticals Inc. said its prescription sleep aid Silenor (doxepin) is now commercially available in the United States.

The specialty pharmaceutical company said Tuesday that it has implemented a wholesale and retail stocking program to disseminate Silenor 3 mg and 6 mg dosepacks to pharmacies nationwide.

Silenor oral tablets, which gained approval in March, are indicated for the treatment of insomnia characterized by difficulty with sleep maintenance.

Late last month, Somaxon unveiled a a co-promotion agreement with Procter & Gamble Co. for Silenor. Under the pact, Somaxon and P&G will co-promote the medication in the U.S. market, with P&G’s professional health care sales force promoting Silenor to targeted primary care and other high-prescribing physicians and Somaxon focusing on specialists and other physicians who treat insomnia. P&G also will promote Silenor to targeted pharmacies and has been granted a right of first negotiation relating to rights to develop and market Silenor as an over-the-counter medication in the United States.

Richard Pascoe, Somaxon president and chief executive officer, noted that a field-sales promotion of Silenor is slated to kick off later this month.

"The commercial availability of Silenor, the first and only prescription product approved for the treatment of sleep maintenance insomnia that is not a controlled substance, is an important milestone for Somaxon and marks the completion of our product launch preparations," Pascoe said in a statement. "We look forward to promoting this highly differentiated product to health care providers alongside our co-promotion partner, Procter & Gamble. Our combined sales teams will begin full-scale, field-based promotion of the product on Sept. 20, 2010, targeting approximately 35,000 physicians and 25,000 pharmacies across the U.S."

Plans also call for a comprehensive marketing program that will utilize web-based initiatives and be directed at doctors physicians not called on directly by the sales force as well as patients suffering from sleep maintenance insomnia, added Pascoe. "This campaign will highlight the traits that we believe will position Silenor for success in the insomnia market — the ability to treat sleep maintenance insomnia into the final hours of the night without meaningful next-day residual effects and without abuse potential," he stated.