Comparative bioavailability of gemfibrozil capsules commercially available in Thailand

Abstract

Four brands of gemfibrozil capsules commercially available in Thailand were evaluated. In vitro studies indicated that all brands met the requirement of the United States Pharmacopoeia XXII. The dissolution rate constants of all brands in phosphate buffer CpH 7.5 ± 0.1) ranged from 1.89 to 8.78 hr-1. The value of brand A, which was the innovator's product, was statistically significant (p < 0.05) lower than those of brands c and D except that of brand B. The bioavailability of all four brands of gemfibrozil capsules were studied in 12 Thai healthy male volunteers using, a single dose of two 300 mg capsules in a crossover design. Plasma gemfibrozil concentrations were determined using HPLC. Data analysis for relevant pharmacokinetic parameters revealed that there were no statistically significant difference (p > 0.05) for the tmax values among the four brands except the c and AUC values of brand A antxthose of brands B and C. Brands A and D were bioequivalent in terms of both the rate and the extent of drug absorption into general blood circulation. The relative bioavailability with respect to brand A for brands B, C and D were 77.55, 83.74 and 97.90%, respectively. Pharmacokinetic of gemfibrozil capsule was well described by one compartment open model. The absorption rate constants ranged from 1.2 to1.80 hr-1. The elimination rate constant ranged from 0.42 to 0.51 hr-1. The biological half-life varied between 1.40 to 1.67 hr. No statistical correlation (p > 0.05) was found between the in vitro and the in vivo data.