Any of a group of central nervous system depressants with the capacity of relieving anxiety and inducing calmness and sleep. Several such drugs also induce amnesia and muscle relaxation and/ or have anticonvulsant properties. Major classes of sedatives/hypnotics include the benzodiazepines and the barbiturates. Also included are alcohol, buspirone, chloral hydrate, acetylcarbromal, glutethimide, methyprylon, ethchlorvynol, ethinamate, meprobamate, and methaqualone. Some authorities use the term sedatives/hypnotics only for a subclass of these drugs used to calm acutely distressed persons or to induce sleep, and distinguish them from (minor) tranquillizers used for the treatment of anxiety.
Barbiturates have a narrow therapeutic-to-toxic dosage ratio and are lethal in overdose. Their abuse liability is high; physical dependence, including tolerance, develops rapidly. Chloral hydrate, acetylcarbromal, glutethimide, methyprylon, ethchlorvynol, and ethinamate also have a high liability for physical dependence and misuse and are also highly lethal in overdose. Because of such dangers, none of the sedatives/hypnotics should be used chronically for the treatment of insomnia.
All sedatives/hypnotics may impair concentration, memory, and coordination; other frequent effects are hangover, slurred speech, incoordination, unsteady gait, drowsiness, dry mouth, decreased gastrointestinal motility, and lability of mood. A paradoxical reaction of excitement or rage may be produced occasionally. The time before onset of sleep is reduced but REM sleep is suppressed. Withdrawal of the drug concerned may produce a rebound of REM sleep and deterioration of sleep patterns. In consequence, patients treated over a long period can become psychologically and physically dependent on the drug even if they never exceed the prescribed dose. Withdrawal reactions can be severe and may occur after no more than several weeks of moderate use of a sedative/hypnotic or anxiolytic drug. Symptoms of withdrawal include anxiety, irritability, insomnia (often with nightmares), nausea or vomiting, tachycardia, sweating, orthostatic hypotension, hallucinatory misperceptions, muscle cramps, tremors and myoclonic twitches, hyperreflexia, and grand mal seizures that may progress to fatal status epilepticus. A withdrawal delirium may develop, usually within one week of cessation or significant reduction in dosage.
Long-term sedative/hypnotic abuse is likely to produce impairments in memory, verbal and nonverbal learning, speed, and coordination that last long after detoxification and, in some, result in a permanent amnestic disorder. Mental and behavioural disorders due to use of other sedatives or hypnotics (FI3) are distinguished from those due to use of alcohol (FIO) in ICD-I0.