Forest Laboratories Inc., of New York, said it, along with Merz Pharma GmbH & Co. KgaA, of Frankfurt, Germany, and Adamas Pharmaceuticals Inc., of Emeryville, Calif., jointly filed a lawsuit in the U.S. District Court for the District of Delaware against several companies for the infringement of some or all of the patents relating to Forest’s Namenda XR (memantine HCl extended-release capsule) product.