Sedative
Sedative, any of the drugs used to reduce nervous tension or induce sleep. Often referred to as sedative-hypnotic drugs, these substances generally have a calming and relaxing effect on the central nervous system and muscles when taken in small doses, and a hypnotic, or sleep-producing, effect when taken in larger doses. For centuries alcohol and opium were the only substances known to produce these effects, but in recent decades over 50 other substances have been discovered, each differing slightly in its effect on the user. Among the sedatives prescribed for calming patients are the tranquilizers Librium (chlordiazepoxide hydrochloride) and Valium (diazepam), which are commonly used to relieve emotional stress (see Anxiety ; Tranquilizer ). Drugs administered to produce sleep include barbiturates such as secobarbital, pentobarbital, and phenobarbital, which produce short, medium, and prolonged durations of sleep, respectively. Chloral hydrate, paraldehyde, antihistamine , and Quaa