Serum concentration and drug effect after intravenous and rectal administration of diazepam

In a randomized crossover study on sedation in outpatient oral surgery, the relation between the serum profile and the drug effect profile for intravenously (i.v.) and rectally administered diazepam was studied. Both sedation methods were found to be equally efficient at a mean dose of 0.25 mg/kg (range, 0.14-0.45) for i.v. administration, and 0.53 mg/kg (range, 0.50-0.58) for rectal administration. Both the serum concentration and the effect reached their mean peaks at the same time; however, this was 15 min later after rectal sedation than after i.v. sedation. Intravenous administration yielded a significantly higher serum concentration of diazepam at the clinical endpoint than did rectal administration, but the mean effect levels at the clinical endpoint were equal for both sedation methods. No linear correlation between log-serum concentration and the patient's estimation of effect was found.