: any of various derivatives of barbituric acid (as phenobarbital) that are used especially as sedatives, hypnotics, and antispasmodics and are often addictive
Any of a class of heterocyclic compounds based on the parent structure, uric acid, and used in medicine. They depress the central nervous system, acting particularly on certain parts of the brain, though they tend to depress the functioning of all the body's tissues. Long-acting barbiturates (e.g., barbital and phenobarbital) are used to treat epilepsy. Intermediate ones (e.g., amobarbital) are used to treat insomnia, short-acting ones (e.g., pentobarbital) to overcome difficulty in falling asleep (one aspect of insomnia), and ultra-short-acting ones (e.g., thiopental sodium) to induce unconsciousness in surgical patients before administration of other anesthetics. Prolonged use of barbiturates may lead to addiction. Sudden withdrawal can be fatal; addicts must be weaned from the drug under medical supervision. Overdoses can result in coma and even death; barbiturates are particularly dangerous, even at normal doses, when combined with alcoholic beverages.