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Comparative study of bioavailability and clinical efficacy of carbamazepine in epileptic patients
O Silpakit1, M Amornpichetkoon, S Kaojarern
1Division of Neurology, Srithanya Hospital, Nonthaburi, Thailand.
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 (Cmax), mean time to reach maximum concentration (tmax), 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.
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