Azithromycin Quantitation in Human Plasma by High-Performance Liquid Chromatography Coupled to Electrospray Mass Spectrometry: Application to Bioequivalence Study

• Published in: Journal of chromatographic science 2008-07, Vol.46 (6), p.479-484
• Main Authors: Xu, Fengguo, Zhang, Zunjian, Bian, Zuwei, Tian, Yuan, Jiao, Haoyan, Liu, Ying
• Format: Article
• Language: English
• Subjects: Analysis; Anti-Bacterial Agents - blood; Anti-Bacterial Agents - pharmacokinetics; Azithromycin - blood; Azithromycin - pharmacokinetics; Biological and medical sciences; Calibration; Chromatography, High Pressure Liquid - methods; Cross-Over Studies; General pharmacology; Humans; Hydrogen-Ion Concentration; Male; Medical sciences; Pharmacology. Drug treatments; Reproducibility of Results; Sensitivity and Specificity; Spectrometry, Mass, Electrospray Ionization - methods; Therapeutic Equivalency
• ISSN: 0021-9665; 1945-239X
• DOI: 10.1093/chromsci/46.6.479

A sensitive and specific liquid chromatography-electrospray ionization mass spectrometry method is developed and validated for the identification and quantitation of azithromycin in human plasma. After the addition of the internal standard and 1.0M sodium hydroxide solution, plasma samples are extracted with a methylene chloride-ethyl acetate mixture (20:80, v/v). The organic layer is evaporated under a stream of nitrogen at 40°C. The residue is reconstituted with 200 µL of the mobile phase. The compounds are separated on a prepacked Shimadzu Shim-pack VP-ODS C18 (5 µm, 150 mm × 2.0 mm) column using a mixture of acetonitrile-water (65:35) (0.5% triethylamine, pH was adjusted to 6.2 with acetic acid) as the mobile phase. Detection is performed on a single quadrupole mass spectrometer by selected ion monitoring mode via electrospray ionization source. The method is fully validated and linear calibration curves are obtained in the concentration ranges from 5 to 2000 ng/mL. The intra- and interbatch relative standard deviations at four different concentration levels are all < 10%. The limit of detection and quantitation are 2 ng/mL and 5 ng/mL, respectively. The proposed method enables the unambiguous identification and quantitation of azithromycin for pharmacokinetic, bioavailability, or bioequivalence studies.