Simplified method for determination of clarithromycin in human plasma using protein precipitation in a 96-well format and liquid chromatography-tandem mass spectrometry

A simplified method to determine clarithromycin concentrations in human plasma using protein precipitation in a 96-well plate and liquid chromatography-tandem mass spectrometry was developed and validated. Plasma proteins were precipitated with acetonitrile and roxithromycin was used as the internal standard. After vortex mixing and centrifugation, the supernatants were directly injected onto a Phenomenex Luna Phenyl-Hexyl column (50 mm x 2.0 mm ID, 3 microm). The mobile phase consisted of water and methanol (30:70, v/v) containing 0.1% formic acid and 5mM ammonium acetate. The flow rate was 0.22 mL/min and the total run time (injection to injection) was less than 3 min. Detection of the analytes was achieved using positive ion electrospray tandem mass spectrometry in selected reaction monitoring (SRM) mode. The linear standard curve ranged from 100 to 5000 ng/mL and the precision and accuracy (inter- and intra-run) were within 7.9% and 4.9%, respectively. The method was successfully used to determine clarithromycin concentrations in human plasma samples obtained from healthy subjects who were given clarithromycin 500 mg for 3 days. The method is rapid, simple, precise and directly applicable to clarithromycin pharmacokinetic studies.