Impax Laboratories, Inc. (NASDAQ:IPXL) today confirms that Pfizer Inc., Pharmacia & Upjohn Company LLC and Pfizer Health AB (collectively, “Pfizer”) have filed suit for patent infringement against Impax in the United States District Court for the District of New Jersey in connection with Detrol® (tolterodine tartrate) immediate-release, 1 mg and 2 mg tablets.