Canadian Journal of Anesthesia, Vol 29, 16-23, Copyright © 1982 by Canadian Anesthesiologists' Society

The Fate of Phenobarbitone in Children in Hypothermia and at Normal Body Temperature

¹ Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
² Department of Anaesthesia, University of Toronto, Director, Intensive Care Unit, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8

Address correspondence to: Dr. D. Kadar, Department of Pharmacology, University of Toronto, Toronto, Ontario, M5S 1A8.

Four critically injured children receiving large doses of phenobarbitone were studied during hypothermia (30°-31°C) and at normal body temperature. The volume of distribution of phenobarbitone varied from 0.79 to 1.01 litres per kg and the serum t ranged from 36.8 ± 9.4 to 86.2 ± 10.5 hrs. The percentage of dose recovered in urine in 16 days ranged from 40.5 to 65.5 per cent: 2.7 to 12.4 per cent as hydroxyphenobarbitone, 1.7 to 19.7 per cent as conjugated hydroxyphenobarbitone, 6.0 to 22.4 per cent as phenobarbitone-N-glucoside and 17.8 to 23.1 per cent as unchanged drug. After the body temperature was allowed to return to normal the rate of excretion of metabolites increased substantially and the rate of excretion of the unchanged drug decreased markedly. It is concluded that reduction in body temperature influences the volume of distribution, rate of metabolism and excretion of phenobarbitone.

Key Words: PHARMACOKINETICS, Phenobarbitone, hypothermia