Determination of azithromycin in human plasma by LC-MS-MS and its pharmacokinetics

A LC-MS-MS assay has been developed for determinating of azithromycin in human plasma and investigating the pharmacokinetics in Chinese male volunteers following oral administration of a single dose of the capsules (0.5 g). Plasma samples were deproteinated by methanol and a liquid chromatographic-mass-mass spectrometric assay was developed for the determination of azithromycin in human plasma. Assay linearity was obtained in the range of 3.048-1016 microg x L(-1) (r = 0.9995). The recovery of azithromycin from human plasma was more than 90%. The intra- and inter-day precision for four different concentration examined were lower than 15%. Its main pharmacokinetic parameters of AUC(0-144), AUC(0- infinity), Cmax, Tmax, T1/2 and MRT were determined from plasma concentrations for both formulations and found to be in good agreement with the reported values. AUC(0-144), Tmax and Cmax were tested for bioequivalence after log-transformation of data. No significant difference was found based on ANOVA. The test formulation was bioequivalent to the reference formulation and there was no significant difference of Tmax between the test formulation and reference formulation.