Plasma concentration of diazepam and N-desmethyldiazepam in children after a single rectal or intramuscular dose of diazepam

Summary The absorption of diazepam and N-desmethyldiazepam after administration of diazepam solution for parenteral injection per rectum and intramuscularly was studied in 9 children (ages 3–12 years). Rectal administration of diazepam 1 mg/kg led to rapid absorption with plasma levels of 270–320 ng/ml within 5 min, and peak levels of 600–1300 ng/ml 10–60 min after administration. The absorption was comparable to that after intramuscular administration. A second peak in plasma diazepam concentration 6–12 h after dosing was observed in 6 children, which may have been due to mobilization of diazepam from the gastrointestinal mucosa produced by feeding 4 h after administration of the drug. A slowly increasing plasma level of N-desmethyldiazepam was observed during the first 24 h after administration of diazepam.