Daily fluctuation of plasma levels with conventional and controlled-release carbamazepine: correlation with adverse effects.

The pharmacokinetics, tolerability, and efficacy of carbamazepine (CBZ) and the pharmacokinetics of carbamazepine-10, 11-epoxide (CBZE) were studied after chronic administration of a conventional tablet formation or of the controlled-release (CR) formulation of CBZ 400 mg (Tegretol 400) to 20 patients with epilepsy treated with carbamazepine and complaining of intermittent adverse effects. To compare the two formulations at the same doses and dose schedules, the study design had to be open, within-patient, with an initial 4 week period to individually adjust the dosage schedule with conventional CBZ followed by a 4 week period in which the CR formulation was substituted for conventional CBZ at the same daily dose and given by the same schedule. A further 4 week period was also studied to evaluate the same dosage of the CR formulation but given b.