Bioequivalence Study of Two Azithromycin Formulations in Healthy Subjects

The study was conducted to rind out whether the bioavailability of a 500 mg azithromycin (CAS 83905-01-5) tablet (Zycin (R), 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 (AUC(t)), area under the plasma concentration-time curve from time zero to infinity (AUC(Inf)), the peak plasma concentration of the drug (C(max)), time needed to achieve the peak plasma concentration (t(max)), and the elimination half-life (t(1/2)). 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 It post dose, the plasma was separated and the concentrations of azithromycin were determined by a LC-MS/MS method. In this study, the mean AUC(t), AUC(inf), C(max) and t(1/2) of azithromycin from the test drug were 4967.49 ng . h . mL(-1), 5871.74 ng . h . mL(-1), 412.14 ng/mL, and 51.32 h, respectively. The mean AUC(t), AUC(t), AUC(inf), C(max), and t(1/2) of azithromycin from the reference drug were 4276.75 ng . h mL(-1), 5578.12 ng . h . mL(-1), 419.89 ng/mL, and 51.23 h, respectively. The median t(max) 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 AUC(t), 101.27 % (84.97 -120.70 %) for AUCInf, and 97.78 % (84.50 -113.16%) for C(max). 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.