DRUG INFORMATION QUARTERLY Chlormethiazole or chlordiazepoxide in alcohol detoxification

The alcohol withdrawal syndrome is charac terised by symptoms such as anxiety, insomnia, anorexia, nausea, tremor, sweating and distur bances in coordination. These symptoms tend to occur within 6 to 12 hours of alcohol-dependent patients stopping or reducing their alcohol in take. Less frequently, convulsions, hallucinosis and delirium tremens can occur. Delirium tremens (disturbed orientation, visual and auditory hallucinations, paranoid ideation and tremulousness) is the most serious complication of alcohol withdrawal and occurs in up to 5% of patients withdrawing from alcohol. If it is severe or poorly treated, death can occur. In the UK some clinicians use Chlormethiazole while others fa vour chlordiazepoxide. This article will examine and compare the use of these two drugs. In the early 1960s, Chlormethiazole was intro duced for the management of acute alcohol withdrawal. Derived from the thiazole moiety of thiamine, it has sedative, hypnotic and anticonvulsant properties (although it seems to have little effect in the prevention of seizures (Dollery, 1991)). Chlormethiazole appears to work by enhancing gamma-aminobutyric acid (GABA) transmission. It is rapidly absorbed after oral administration but undergoes extensive presystemic metabolism in the liver. The systemic bioavailability is therefore unpredictable but greatly increased in patients with cirrhosis. Chlormethiazole is a short acting drug with a plasma half-life of approximately 4 hours: although this may be increased to up to 9 hours in advanced liver disease and up to 12 hours in the elderly.