An LC-MS/MS Validated Method for Quantification of Chlorzoxazone in Human Plasma and Its Application to a Bioequivalence Study.

ABSTRACT

A simple, sensitive, specific, accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for determination of chlorzoxazone in human plasma was developed and validated to evaluate the pharmacokinetic characteristics of chlorzoxazone test or reference formulation. Sample preparation was achieved by one step protein precipitation and dilution with acetontrile. The chromatographic separation was performed at 40°C with a gradient mobile phase (0.3 mL/min) and a Shimadzu VP-ODS C18 analytical column (column size 150 × 2.0 mm). TSQ quantum access triple-quadrapole MS/MS detection was operated in a negative mode by multiple reaction monitoring. Ion transitions at m/z 168.0→132.1 for chlorzoxazone and m/z 451.3→379.3 for repaglinide (internal standard) were used for the LC-MS/MS analysis. The calibration was linear (r ≥ 0.995) over the tested concentration range of 0.2-20 µg/mL for chlorzoxazone in plasma. Precision, accuracy, recovery, matrix effect and stability for chlorzoxazone were evaluated and were excellent within the range of tested concentrations. This method was successfully applied to a bioequivalence study in 20 healthy Chinese volunteers. This method could also contribute to the personalized medication and therapeutic drug monitoring of chlorzoxazone.