Claim: Cyclobenzaprine is the best-selling muscle relaxant.

Cyclobenzaprine , sold under the brand name Flexeril among others , is a muscle relaxer medication used to relieve skeletal muscle spasms and associated pain in acute musculoskeletal conditions . It is the best-studied drug for this application . It has also been used off-label for fibromyalgia treatment .   As of 2015 the cost for a typical course of medication in the United States is less than .