Comparative Study of Bioavailability and Clinical Efficacy of Carbamazepine in Epileptic Patients

Abstract

OBJECTIVE:

To compare the bioavailability of three generic brands of carbamazepine tablets with that of a proprietary brand in adult patients with epilepsy.

DESIGN:

A double-blind, randomized, three-phase crossover study.

SETTING:

A psychiatric facility.

PARTICIPANTS:

Eighteen patients with epilepsy who had taken carbamazepine at least 5 months before entering the study.

MAIN OUTCOME MEASURES:

Ten blood specimens from each patient were collected at steady-state. Plasma concentration of carbamazepine was analyzed for pharmacokinetic parameters such as maximum plasma concentration (C_max), mean time to reach maximum concentration (t_max), and mean AUC.

RESULTS:

There were no statistically significant differences in these parameters among four brands of carbamazepine. However, when comparing the 90% CI of AUC of three generic brands with that of the proprietary brand, the AUC of two generic brands lay within a range of 80% to 120%. The effects of gender and each brand of carbamazepine on these pharmacokinetic parameters were also analyzed. Breakthrough seizures occurred even though the plasma concentration of carbamazepine was therapeutic.

CONCLUSIONS:

The bioavailability of two generic brands of carbamazepine tablets (Carmapine and Carzepine) and the proprietary brand (Tegretol) were equivalent in this sample of adult patients with epilepsy.