Barbiturate

Barbiturate, any of an important group of drugs that depress brain function; they are derived from barbituric acid (C4H4N2O3), a combination of urea and malonic acid. Depending on the dosage or formulation, barbiturates have a sedative (tranquilizing), hypnotic (sleep-inducing), anticonvulsant, or anesthetic effect. Very short-acting barbiturates such as thiopental are injected intravenously to induce rapid anesthesia before surgery. Phenobarbital, a long-acting barbiturate, is prescribed with other medications to prevent epileptic seizures. Other barbituric-acid derivatives, such as secobarbital, were used as antianxiety medications until the development of the tranquilizer; they are still in use for the short-term treatment of insomnia, although tranquilizers are more suitable sleep inducers. Barbiturates are common drugs of abuse. Taken orally or intravenously, they produce symptoms similar to drunkenness: loss of inhibition, boisterous or violent behavior, muscle incoordination, depression, and sedation. They are physically addicting and produce severe withdrawal symptoms; overdoses can cause profound shock, coma, or death. See Drug Dependence.