Barbiturate, any of a group of drugs, derived from bituric acid, that act as sedatives, anesthetics, or anticonvulsants in the central nervous system by depressing nerve cell activity. Widely prescribed in the past for insomnia, their use is now discouraged because of high rates of addiction and the danger of overdose. Phenobarbital is used in the treatment of convulsions. Overdoses of barbiturates cause the deep and rapid onset of coma and can be fatal, especially when combined with alcohol.
See also: Drug.