Demoxepam is a major pharmacologically active metabolite of the benzodiazepine chlordiazepoxide, the first drug within the class to gain approval by the Food and Drug Administration for use as an anticonvulsant, muscle relaxant and sedative hypnotic. Demoxepam has been shown to have antianxiety activity in man. The eventual elimination of demoxepam from the plasma was slow, with a range in half-life of 14-95 hr. The half-life of demoxepam was markedly longer than that of chlordiazepoxide. Demoxepam has an inhibitory effect on in vitro [3H]tryptophan binding to rat hepatic nuclei.