Impax Laboratories, Inc announced that Eurand, Inc, Cephalon, Inc, and Anesta AG have filed suit for patent infringement in the United States District Court for the District of Delaware based on the company's submission of Abbreviated New Drug Application (ANDA) for cyclobenzaprine hydrochloride extended release capsules (15 and 30 mg), generic of Amrix, to the Food and Drug Administration. In connection with this ANDA, Impax provided notice that its submission includes a Paragraph IV certification stating the company believes its product does not infringe US Patent No 7,387,793, or the patent is invalid or unenforceable.

Amrix is indicated as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions. According to Wolters Kluwer Health, US sales of Amrix were approximately $54 million in the 12 months ended November 30, 2008.

Impax Laboratories is a technology based specialty pharmaceutical company applying its formulation expertise and drug delivery technology to the development of controlled-release and specialty generics in addition to the development of branded products.