Metaxalone is a muscle relaxant used to relax muscles and relieve pain caused by strains, sprains, and other musculoskeletal conditions. It is considered to be a moderately strong muscle relaxant. Skelaxin comes in two dosages, a 400mg tablet and an 800mg tablet.
Metaxalone is marketed by King Pharmaceuticals under the brand name Skelaxin. It is still under patent to King and thus is not available in a generic form. Specific information about the patent held by King does not seem to be publicly available; therefore, no off-patent date can be established. The patent appears to have been established at the very latest in 1964 (and possibly earlier based on a USPTO search for metaxalone according to King's product info [http://www.kingpharm.com/product_view.asp?id_product=101, which contradicts the usual 10-year patent rights granted for new drugs to pharmacutical companies by the FDA.

Metaxalone - FamilyDoctor.org - Information for consumers in English or Spanish.