Development of a LC–MS/MS-based method for determining metolazone concentrations in human plasma: Application to a pharmacokinetic study

摘要

Abstract In this study, a method was developed and validated for the quantification of metolazone in human plasma samples. This method involves high-performance liquid chromatography coupled with tandem mass spectrometry and is more sensitive, selective and rapid than currently available methods. Chromatography was performed using a Phenomenex? Luna {C18} column (100?mm?×?2.0?mm, 5?μm, 100??) with an isocratic mobile phase of 0.1% formic acid:acetonitrile (40:60, v/v) and zaleplon as an internal standard. The drug and internal standard were extracted by liquid–liquid extraction and analyzed by mass spectrometry in the multiple reaction monitoring mode by using m/z values of 366.20/259.10 for metolazone and 306.20/235.60 for zaleplon. The calibration curve was linear over metolazone concentrations ranging from 0.02?ng/mL to 15?ng/mL. The lower limit of quantification was 0.02?ng/mL. Intra- and inter-assay precisions were 0.9–4.8% and 4.2–6.3%, respectively. The intra- and inter-assay accuracies in quantifying metolazone were 97.5–102.3% and 99.2–104.0%, respectively. Metolazone and zaleplon were eluted within 3.6 minutes, and the retention time was 1.75 minutes for metolazone and zaleplon. The validated method was successfully applied to a pharmacokinetic study of metolazone in human plasma.