(bärbĭch'Әrāt´´), any one of a group of drugs that act as depressants on the central nervous system. High doses depress both nerve and muscle activity and inhibit oxygen consumption in the tissues. In low doses barbiturates act as sedatives, i.e., they have a tranquilizing effect; increased doses have a hypnotic or sleep-inducing effect; still larger doses have anticonvulsant and anesthetic activity. The mechanism of action on the central nervous system is not known. The barbiturates are all derivatives of barbituric acid, which was first prepared in 1864 by the German organic chemist Adolf von Baeyer.
The drugs differ widely in the duration of their action, which depends on the rapidity with which they are distributed in body tissues, degraded, and excreted. Ultrashort-acting barbiturates such as thiopental sodium (Pentothal) are often used as general anesthetics. Secobarbital (Seconal) and pentobarbital sodium (Nembutal) are short-acting barbiturates, amobarbital (Amytal) is intermediate in duration of action, and phenobarbital (Luminal) is a long-acting derivative.
Barbiturates are used to relax patients before surgery, as anticonvulsants, and as sleeping pills. They also are commonly abused. Taken regularly, barbiturates can be psychologically and physically addictive (see drug addiction and drug abuse). Barbiturate addicts must be withdrawn from the drug gradually to avoid severe withdrawal symptoms such as convulsions. Overdose can cause coma or death. In the United States the manufacture and distribution of barbiturates were brought under federal control by the 1965 Drug Abuse and Control Act, and they are legally available only by prescription.
See publications of the Drugs & Crime Data Center and Clearinghouse, the Bureau of Justice Statistics Clearinghouse, and the National Clearinghouse for Alcohol and Drug Information.