Methocarbamol is a central muscle relaxant for skeletal muscles, used to treat spasms. It is structurally related to guaifenesin. Methocarbamol's exact mechanism of causing skeletal muscle relaxation is unknown. It is thought to work centrally, perhaps by general depressant effects. It has no direct relaxant effects on striated muscle, nerve fibers, or the motor endplate. It will not directly relax contracted skeletal muscles. The drug has a secondary sedative effect. Methocarbamol is used for use as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions. Under the trade name Robaxin, Methocarbamol is marketed by Actient Pharmaceuticals in the United States and Pfizer in Canada.