Metaxalone ( 5-[(3,5-dimethylphenoxy) methyl]-2-oxazolidinone ) is a prescription-only drug used to treat acute, painful musculoskeletal conditions, such as muscles in spasm, strains, sprains etc.
It has been sold in the US since 1962 under the brand name Skelaxin.
The mechanism of action of metaxalone in humans has not been established but may be due to general central nervous system depression.
Source US Patent 7,378,434