Distribution of carbamazepine and its epoxide in blood compartments in adolescent and adult epileptic patients.

Carbamazepine (CBZ) used in the treatment of epilepsy, is metabolized in man to an active metabolite: carbamazepine 10-11 epoxide (CBZ-E). CBZ and CBZ-E concentrations in the different blood compartments (plasma ultrafiltrate, plasma proteins, and red blood cells (RBC)) of epileptic patients on CBZ monotherapy were assessed using HPLC. The highest CBZ and CBZ-E level to dose ratios were observed in the RBC. For CBZ and CBZ-E significant correlations were found between some blood compartments particularly between RBC and plasma ultrafiltrate. The measurement of CBZ and CBZ-E in all blood compartments may be interesting in uncontrolled patients and in patients presenting side-effects which cannot be explained by total plasma concentration values.