Carbamazepine 10,11-epoxide in children.

Concentrations of carbamazepine (CBZ) and its 10,11-epoxide metabolite (CBZ-E) were measured in simultaneously collected plasma and mixed saliva samples from 15 children (aged 1-13 years). Saliva concentrations of CBZ and CBZ-E were measured in hourly samples taken from six of these children during dose intervals whilst on different dose or dose-frequency regimens. Saliva and plasma CBZ (r = 0.91; P less than 0.001) and CBZ-E (r = 0.91; P less than 0.001) concentrations were significantly correlated. The mean +/- s.d. steady state CBZ-E/CBZ concentration ratio in the six children was 0.40 +/- 0.21 and was similar at all times within the 12 h dose interval. The mean +/- s.d. percentage fluctuation of the combined CBZ + CBZ-E (103.0 +/-28.9) was significantly less than that of CBZ-E (145.5 +/- 52.8) but not CBZ (109.6 +/- 31.1). If CBZ and CBZ-E have equipotent anticonvulsant activity in man, the contribution of CBZ-E approximates to 30% of total anticonvulsant effect in children taking CBZ alone.