[Plasma concentrations and clinical activity of benzodiazepines]

After ingestion of equal doses of a given benzodiazepine serum concentrations vary greatly from one individual to another, suggesting that it may be advisable to monitor circulating drug levels. But so far, few studies have been conducted on the relation between benzodiazepine serum concentrations and clinical results. In general, these studies conclude that there is no significant relation between circulating drug levels and anxiolytic activity. On the other hand, the kinetic properties of benzodiazepines determine the type, rapidity of onset and duration of action of each drug. Onset of action depends on the speed of absorption of the product, and duration of action depends on how widely it is diffused. After administration of repeated doses of a benzodiazepine, accumulation of the drug depends on its half-life of elimination and metabolic clearance. Finally, the side-effects of benzodiazepines are often related to their concentrations in the plasma, but in cases of massive intoxication, there is often a dissociation between drug serum levels and the clinical picture.