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Abstract
A simple, sensitive, selective, and reproducible method based on high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (LC/MS) was developed for the determination of a macrolide antibiotic azithromycin in human plasma. The internal standard (roxithromycin) was separated from azithromycin on a Hypersil Gold C18 column, with retention times of 10.71 and 13.67 min, respectively. The mobile phase consisted of a mixture of 20 mM ammonium acetate buffer (pH 5.2), acetonitrile and methanol (50:40:10, v/v/v), running through the column at a flow rate of 0.3 mL/min. The chromatographic analysis was operated at 25°C. Sample preparation was prepared by liquid-liquid extraction with a mixture of 7:3 (v/v) diethylether:dichloromethane. The precision of the method based on within-day repeatability and reproducibility (day-to-day variation) was below 5% (% coefficient of variations: % CV). Good accuracy was observed for both the intra-day or inter-day assays. Limit of quantification was accepted as 1 ng using 200 μL plasma samples. The mean recoveries for azithromycin and the internal standard were greater than 85%. The method was applied successfully to the investigation of the pharmacokinetics of azithromycin when given in combination with fosmidomycin as oral doses of 750 mg twelve hourly for 3 days in a total of 5 Thai male patients with acute uncomplicated falciparum malaria.
ACKNOWLEDGMENT
This investigation received financial support from Jomaa Pharma Gmblt Company, Germany and the Commission on Higher Education, Ministry of Education, Thailand.
Notes
% CV: coefficient of variation; % DMV: deviation of mean value from the theoretical value.