Beta-erythroidine is an organic heterotetracyclic indole alkaloid isolated from the seeds and other parts of Erythrina species. 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. Beta-erythroidine is a neuronal nicotinic acetylcholine receptor antagonist. The beta-erythroidine and its more potent derivative (2,7-dihydro) have been used as muscular relaxants in numerous clinical applications. This activity is attributed to a antagonistic action of the dihydro-beta-erythroidine with the nicotinic receptors of acetyl choline.