Bioequivalence study of two azithromycin formulations in healthy subjects.

The study was conducted to find out whether the bioavailability of a 500 mg azithromycin (CAS 83905-01-5) tablet (Zycin, test) was equivalent to that of a reference formulation. The pharmacokinetic parameters assessed in this study were the area under the plasma concentration-time curve from time zero to 120 h (AUCt), area under the plasma concentration-time curve from time zero to infinity (AUCinf), the peak plasma concentration of the drug (Cmax), time needed to achieve the peak plasma concentration (tmax), and the elimination half-life (t1/2). This was a randomized, single blind, two-period, cross-over study which included 18 healthy adult male and female subjects under fasting conditions. In each of the two study periods (separated by a washout of two weeks) a single dose of test or reference drug was administered. Blood samples were taken up to 120 h post dose, the plasma was separated and the concentrations of azithromycin were determined by a LC-MS/MS method. In this study, the mean AUCt, AUCinf, Cmax, and t1/2 of azithromycin from the test drug were 4967.49 ng x h x mL(-1), 5871.74 ng x h x mL(-1), 412.14 ng/mL, and 51.32 h, respectively. The mean AUCt, AUCinf, Cmax, and t1/2 of azithromycin from the reference drug were 4276.75 ng x h x mL(-1), 5578.12 ng x h x mL(-1), 419.89 ng/mL, and 51.23 h, respectively. The median tmax of he test drug and reference drug were 3.0 h and 2.0 h, respectively. The geometric mean ratios (90% CI) of the test drug/reference drug for azithromycin were 101.56% (86.61-119.08%) for AUCt, 101.27% (84.97-120.70%) for AUCinf, and 97.78% (84.50-113.16%) for Cmax. Based on this study, it was concluded that the two azithromycin tablets (test and reference drug) were bioequivalent in terms of the rate and extent of absorption.