Chlormethiazole is a sedative and hypnotic that is widely used in treating and preventing symptoms of acute alcohol withdrawal. It is a drug which is structurally related to thiamine (vitamin B1) but acts like a barbiturate, that is, a sedative, hypnotic, muscle relaxant and anticonvulsant. A sedative is a drug that depresses the central nervous system (CNS), which causes calmness, relaxation, reduction of anxiety, sleepiness, slowed breathing, slurred speech, staggering gait, poor judgment, and slow, uncertain reflexes. ... Hypnotic drugs are a class of drugs that induce sleep, used in the treatment of severe insomnia. ... Thiamine mononitrate Thiamine or thiamin, also known as vitamin B1, is a colorless compound with chemical formula C12H17N4OS. It is soluble in water and insoluble in alcohol. ... Barbiturates are drugs that act as central nervous system (CNS) depressants, and by virtue of this they produce a wide spectrum of effects, from mild sedation to anesthesia. ...

The drug acts on receptors in the brain known as GABA receptors, which cause the release of a chemical called GABA (gamma-aminobutyric acid). GABA is a major inhibitory chemical in the brain involved in causing sleepiness and controlling anxiety and fits. It acts by increasing the activity of GABA, thereby reducing the functioning of certain areas of the brain. This results in sleepiness, a decrease in anxiety and relaxation of muscles. It also inhibits a chemical called alcohol dehydrogenase that is responsible for breaking down alcohol in the body. This slows the rate of elimination of alcohol from the body, which helps to relieve the sudden effects of alcohol withdrawal in alcoholics. The GABA receptors are a group of receptors with γ-aminobutyric acid (GABA) as their endogenous ligand. ... Chemical structure of GABA Gamma-aminobutyric acid (GABA) is a neurotransmitter in widely divergent species. ...

It is also used for the management of agitation, restlessness, short term insomnia and Parkinson's disease in the elderly.

This medicine may cause drowsiness. If affected do not drive or operate machinery. Alcohol should be avoided. Tolerance and dependence readily occur to this medicine. Tolerance means that less effect is achieved from the same dose. Dependence means that the patient finds it very difficult to stop using the medicine. Abrupt withdrawal may result in symtoms similar to those of sudden withdrawal of alcohol.

In the U.S it is sold under the brand, Distraneurin® (AstraZeneca Pharmaceuticals) and in the U.K, Heminevrin® (AstraZeneca Pharmaceuticals). AstraZeneca PLC (LSE: AZN), is a large Anglo-Swedish pharmaceutical company formed on 6 April 1999 by the merger of Swedish Astra AB and British Zeneca Group PLC. Zeneca was part of Imperial Chemical Industries prior to a demerger in 1993. ...