The fate of phenobarbitone in children in hypothermia and at normal body temperature.

Four critically injured children receiving large doses of phenobarbitone were studied during hypothermia (30 degrees - 31 degrees 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 1/2 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.