A drug used to produce muscle relaxation (excepting neuromuscular blocking agents). Its primary clinical and therapeutic use is the treatment of muscle spasm and immobility associated with strains, sprains, and injuries of the back and, to a lesser degree, injuries to the neck. Also used for the treatment of a variety of clinical conditions that have in common only the presence of skeletal muscle hyperactivity, for example, the muscle spasms that can occur in multiple sclerosis.
Obtained from the bark of Cinchona species, quinine was the first effective anti-malarial. Other uses include treatment of certain muscular disorders, such as nocturnal leg cramps and congenital myotonia, and giving the characteristic bitter taste to tonic water.