Plasma concentrations of medazepam and its metabolites after oral administration.

The plasma concentrations of medazepam and its metabolites, diazepam and desmethyldiazepam, were determined in volunteer subjects following the oral administration of medazepam 10 mg. The results indicated that medazepam was absorbed rapidly, that low concentrations of metabolites were present during the 1st h, and that the build-up in the circulation of the major metabolite, desmethyldiazepam, was prolonged and variable. As many of the clinical effects and possible adverse reactions of medazepam appear to be associated with the presence of this major metabolite, the metabolic and pharmacokinetic characteristics of the drug should be considered when using medazepam as an anxiolytic before dentistry or surgery.