Bioequivalence of roxithromycin tablets

Three brands of 150 mg roxithromycin tablets were evaluated. In vitro studies indicated that all brands met the general requirements of the United States Pharmacopoeia XXIII for content of active ingredient, uniformity of dosage units and disintegration test. The dissolution rate constants of all brands in phosphate buffer (pH 7.4± 0.1) ranged from 1.31 to 1.85 hr-1. The value of brand C showed statistically significant (p < 0.05) lower than those of brands A and B. Comparative bioavailability of brands B and C relative to brand A of 150 mg roxithromycin tablet were conducted in 12 healthy Thai male volunteers using a single dose of 150 mg tablets in a crossover design. Blood sample were collected at appropriate time interval post dose. Plasm a roxithromycin concentrations were determined via microbiological technique. Individual plasm a roxithromycin concentration-time profile was analyzed for relevant pharmacokinetic parameters. Data analysis revealed that there were no statistically significant differences (p > 0 .0 5) among the corresponding pharmacokinetic parameters; C max, t max and AUC values of all three brands. Also, the ratios of individual parameter of brands B and C to that of brand A were within 80-125% of 90% confidence interval. These implied that brands B and C were bioequivalent with brand A in terms of both the rate and the amount of drug absorption. The pharmacokinetic of 150 mg roxithromycin tablet was described by two compartment open model with first order absorption and first order elimination. The absorption rate constants were between 0.54 to 0.66 hr-1, the eliminate rate constants were between 0.10 to 0.11 hr-1, and the elimination half-life varied between 6.60 to 7.01 hr.