[Concept of half-life and benzodiazepine metabolism. Critical study].

About twenty five benzodiazepines are widely used around the world. The compounds differ essentially by the rate and the extent of their appearance in the systemic circulation and their distribution in the body and by the rates and the steps of their metabolism. The duration of action for benzodiazepines have been described using the beta elimination half-lives. However, this parameter is only one of the several factors involved in the drug disappearance during the clinical effect period. But it can provide some informations on the likelihood of accumulation. One question of tremendous importance for the clinical practice remains the amount and the activity of the benzodiazepines metabolites. Extended studies appear crucial for the potential clinical benefits of this class of compounds.