Barr Pharmaceuticals, Inc. confirmed that its subsidiary, Barr Laboratories, Inc., has initiated a patent challenge for sanofi-aventis US LLC's Ambien CR (Zolpidem Tartrate Extended-Release Tablets), 6.25mg & 12.5mg.

Barr filed its Abbreviated New Drug Application (ANDA) containing a paragraph IV certification for a generic Ambien CR product with the US Food & Drug Administration (FDA) in December 2006, and received notification of the application's acceptance for filing in February 2007. Following receipt of the notice from the FDA, Barr notified sanofi-aventis, the New Drug Application (NDA) and patent owner.

On April 5, 2007, sanofi-aventis filed suit in the US District Court of New Jersey to prevent Barr from proceeding with the commercialization of its product. This action formally initiates the patent challenge process under the Hatch-Waxman Act.

Ambien CR (Zolpidem Tartrate Extended-Release Tablets) 6.25mg & 12.5mg is indicated for the treatment of insomnia, characterized by difficulties with sleep onset and/or sleep maintenance (as measured by wake time after sleep onset). The product had sales of approximately $659 million in the US, based on IMS sales data for the twelve months ended February 2007.

Barr Pharmaceuticals, Inc. is a global specialty pharmaceutical company that operates in more than 30 countries worldwide and is engaged in the development, manufacture and marketing of generic and proprietary pharmaceuticals, biopharmaceuticals and active pharmaceutical ingredients.