Cerebrospinal‐Fluid Concentrations of Diazepam and its Metabolites in Man

Abstract: Plasma and cerebrospinal‐fluid (CSF) concentrations of diazepam, its main metabolite, N‐demethyldiazepam, and free oxazepam were studied gas chromatographically in 49 patients suffering from neurological diseases, after a 10 mg intramuscular dose of diazepam. These determinations were made in three other patients after repeated intramuscular doses of 10 mg diazepam. In seven of the patients both free and plasma protein‐bound diazepam, and N‐demethyldiazepam were determined by ultracentrifugation after a single dose of 10 mg intramuscular diazepam. After a single dose of diazepam there was only 2–3% of the total plasma concentration of diazepam and 1–4% of that of N‐demethyldiazepam in the CSF. After repeated doses of diazepam the same values were 3% and 4%, respectively. The plasma protein binding capacity of diazepam was 98% and that of N‐demethyl‐diazepam 97%. Free diazepam and N‐demethyldiazepam concentrations in the plasma were in equilibrium with their CSF concentrations. No accumulation of diazepam and N‐demethyldiazepam could be found in the CSF. No free oxazepam was found.