Microsomal enzyme induction in children: the influence of carbamazepine treatment on antipyrine kinetics, 6 beta-hydroxycortisol excretion and plasma gamma-glutamyltranspeptidase activity.

1 The influence of carbamazepine (CBZ) therapy on saliva antipyrine kinetics, urinary 6 beta-hydroxycortisol excretion and plasma gamma-glutamyltranspeptidase activity was determined in nine children aged 6-14 years. 2 During 5 weeks of CBZ therapy the mean (+/- s.d.) antipyrine clearance increased from 65 +/- 12 ml kg-1 h-1 to 143 +/- 34 ml kg-1 h-1 (P less than 0.001) and the mean half-life declined from 6.24 +/- 1.23 h to 2.78 +/- 0.59 h (P less than 0.001). The apparent volume of distribution of antipyrine did not change during CBZ treatment. 3 Urinary 6 beta-hydroxycortisol excretion increased markedly during the study period from 5.10 +/- 1.77 micrograms day-1 kg-1 to 17.85 +/- 6.75 micrograms day-1 kg-1 (P less than 0.01). 4 Plasma gamma-glutamyltranspeptidase activity increased in eight out of nine children during CBZ therapy but the change was not statistically significant. 5 CBZ appears to have a marked enzyme inducing effect in young epileptics as indicated by antipyrine kinetics and 6 beta-hydroxycortisol excretion.