Bioavailability of norfloxacin tablets commercially available in Thailand

Abstract

Six brands of 400 mg norfloxacin tablets were evaluated. In vitro studies indicated that all brands excepts brand C met the requirements of the British Pharmacopoeia 1988 and the United State Pharmacopoeia XXII for disintegration time and dissolution test, respectively. The dissolution rate constants of all brands in buffer pH 4.0 ranged from 0.52 to 13.97 hr⁻¹. The value of brand a was statistically significant difference (p < 0.05) from those of brands C and E. The bioavailability of four brands of norfloxacin tablets with difference in dissolution rates were studied in twelve healthy Thai male subjects using, a single dose of 400 mg in a crossover design. Plasma norfloxacin concentrations were determined using HPLC. Data analysis by CSTRIP computer program revealed that there were no statistically significant differences (p > 0.05) for the T[subscript max] values among the four brands except for the C[subscript max] and AUC values. Brands A, B and D were bioequivalent. The relative bioavailability with respect to brand A for brands B, C and D were 120.88, 50.46 and 115.77% respectively. Pharmacokinetics of norfloxacin tablet was best described by a two-compartment open model with first order absorption and elimination. The absorption rate constants ranged from 1.46 to 1.96 hr⁻¹. The biological half-life varied between 3.98 to 5.36 hr. Correlation studies between the in vitro with the in vivo data showed that only the disintegration times was likely to be correlative with the maximum concentration.