Quantitative determination of azithromycin in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study

J Pharm Biomed Anal. 2006 Oct 11;42(4):480-7. doi: 10.1016/j.jpba.2006.05.011. Epub 2006 Jul 5.


A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for determination of azithromycin in human plasma was developed and validated. Azithromycin in plasma (0.2mL) was extracted with methyl tert-butyl ether-hexane (50:50, v/v), organic phase was transferred to another clear 1.5mL Eppendorf tube and evaporated to dryness at 40 degrees C and dissolved in mobile phase, samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150mmx2.1mm i.d., 5microm), together with a mobile phase containing of 20mM ammonium acetate (pH 5.2)-acetonitrile-methanol (50:40:10, v/v/v) and was isocratically eluted at a flow rate of 0.2mL/min. Azithromycin and its internal standard, clarithromycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 2 to 1000ng/mL with r=0.9977. The limit of quantification for azithromycin in plasma was 2ng/mL with good accuracy and precision. The higher mean extraction recovery, say 81.2% and 75.5% for azithromycin and internal standard (IS), respectively, was obtained in this work. The intra-day and inter-day precision ranged from 4.8% to 8.6% and 6.4% to 10.7% (R.S.D.), respectively. The established method has been successfully applied to bioequivalence study of 2 azithromycin formulations for 24 healthy volunteers.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Administration, Oral
  • Adult
  • Anti-Bacterial Agents / chemistry
  • Anti-Bacterial Agents / pharmacokinetics
  • Azithromycin / administration & dosage
  • Azithromycin / blood
  • Azithromycin / chemistry*
  • Azithromycin / pharmacokinetics*
  • Chromatography, High Pressure Liquid / methods*
  • Clarithromycin / chemistry
  • Clarithromycin / pharmacokinetics
  • Humans
  • Male
  • Reproducibility of Results
  • Spectrometry, Mass, Electrospray Ionization / methods*
  • Therapeutic Equivalency


  • Anti-Bacterial Agents
  • Azithromycin
  • Clarithromycin