Pharmacokinetic and clinical considerations in the choice of a hypnotic.

Not only has insomnia become much more frequent in the last hundred years but its causes have also changed considerably. In the treatment of insomnia, benzodiazepines--because of their additional anxiolytic effect--offer substantial advantages over other sleep-inducing agents. The residual fraction--the quotient of plasma concentration at 12 h after drug intake to maximum plasma concentration--makes it possible to differentiate between the benzodiazepines according to their suitability as anxiolytics or hypnotics. Midazolam has the lowest residual fraction of all known benzodiazepines and thus, administered in the appropriate dosage, also has the shortest duration of activity.