Bioequivalence of Two Formulations of a Single Oral Dose of 500-mg Azithromycin Granules: A Randomized, Open-Label, Two-Period Crossover Study in Healthy Han Chinese Volunteers

Background: In recent years, the use of generic drugs has been increasing due to their effectiveness and to the increasing variety of drugs that are now available in generic formulations. Although several generic oral formulations of azithromycin are available in China, information concerning the bioavailability of these formulations in the Chinese population is unavailable.Objective: The purpose of this study was to compare the bioequivalence and tolerability of a single oral dose of 2 commercial brands of 500-mg azithromycin granules in healthy Han Chinese volunteers.Methods: In a randomized, open-label, 2-period crossover study, the bioequivalence and tolerability of 2 commercial formulations of azithromycin granules (test: Dayin Ocean Biochemical Company Ltd., Shandong, China; reference: Taiyang Drug Company Ltd., Beijing, China) were compared in healthy adult Han Chinese volunteers. Both the test and the reference formulations were administered to each subject. The 2 treatment phases were separated by a 3-week washout period. Liquid chromatography-tandem mass spectrometry was used to determine plasma drug concentrations. The formulations were considered bioequivalent if the natural log-transformed ratios of C_max and AUC were within the predetermined equivalence range of 70% to 143% and 80% to 125%, respectively, and if P ≤ 0.05 for the 90% CIs.Results: Twenty-four male Han Chinese volunteers (mean [SD] age, 21.0 [2.0] years [range, 18-25 years]; mean [SD] weight, 67.6 [5.6] kg [range, 56-81 kg]; mean [SD] height, 176.0 [5.0] cm [range, 165-188 cm]) were enrolled. Twenty-two subjects completed the study, with 2 withdrawing for personal reasons. No period or sequence effect was observed. The 90% CIs for the corresponding ratios of C_max, AUC from hour 0 to time t, and AUC from hour 0 to any time point were 85.9 to 103.9, 83.6 to 106.0, and 84.7 to 105.9 (in the 2 one-sided t tests; all, P < 0.05), respectively. Similar results were found in data without a logarithmic transformation. There were no significant differences in the plasma concentration-time curves of the test and reference formulations. No adverse events were reported by the subjects or revealed by clinical or laboratory tests.Conclusions: Single oral doses of 2 commercial brands of azithromycin granules (500 mg) were equivalent with regard to the rate and extent of absorption among these healthy Han Chinese volunteers. Both formulations were well tolerated.