Cephalon agrees to buy muscle relaxant drug

NEW YORK, Aug 23 (Reuters) - Cephalon Inc. (CEPH.O) said on Thursday it agreed to pay $100 million in cash and possibly other future payments to acquire North American rights to the recently approved muscle spasm drug Amrix.

Cephalon said it was buying the rights for the extended-release medication from privately held ECR Pharmaceuticals.

Two dosage strengths of the drug were approved by U.S. regulators in February for short-term use, accompanied by rest and physical therapy, to treat muscle spasm associated with acute musculoskeletal conditions, Cephalon said. The drug has not yet been introduced, however, in the United States.

Cephalon, which sells the narcolepsy drug Provigil, said it expects to launch Amrix early in the fourth quarter in the United States.