Prolonged recovery after diazepam sedation: the influence of food, charcoal ingestion and injection rate on the effects of intravenous diazepam.

Thirteen subjects received diazepam 0.3 mg/kg i.v. twice with a 2-week interval between the doses. In seven subjects who had eaten at 3 h after the injection, reactive skills in a choice reaction test were impaired significantly (P less than 0.05) and there was a 20% increase in the serum diazepam concentrations at 5 h. When the meal was eaten at 7 h, a 50% increase (P less than 0.01) in the serum diazepam concentration was not associated with a significant impairment in psychomotor skills. In a second group of six subjects charcoal ingestion failed to hasten the clearance of diazepam from serum, and did not affect recovery of co-ordinative skills. In a third group of 12 subjects receiving diazepam 0.15 mg/kg i.v. twice at an interval of 2 weeks, the rapid injection of diazepam resulted in a significantly greater (P less than 0.05) degree of drooping of the upper eyelid and in a greater incidence of amnesia to abdominal pinching. The subjects also experienced more pain in the arm during the faster injection (P less than 0.01). Late effects on psychomotor skills were similar with both rates of injection. The results suggest that the remobilization of diazepam from its storage site after food intake induces a late impairment of psychomotor skills, especially if the food is eaten within less than 5 h after the injection. A rapid i.v. injection of diazepam induces greater sedative and amnesic effects than a slow injection of the same dose, but the slow injection of a greater dose is preferable because of the possibility of thrombophlebitis after rapid injection.