Simultaneous Determination of Chlorzoxazone and Midazolam in Rat Plasma by HPLC

Objective:To establish an HPLC method for the simultaneous determination of probe drugs(chlorzoxazone and midazolam) in rat plasma.Methods:An Inertsil-C18 column(250 mm×4.6 mm,5 μm) was used and the mobile phase consisted of acetonitrile-20 mmol·L-1 ammonium acetate-acetic acid(45:55:0.1,v/v) with the flow rate of 1 mL·min-1.The detection wavelength was 210 nm and the column oven was kept at 40℃.Results:Linear ranges of chlorzoxazone and midazolam in rat plasma were both 0.05～30 μg·mL-1.The limit of detection were both 0.05 μg·mL-1;and average methodological recoveries were 96.47%±4.35%,112.56%±4.05% and 112.64%±4.28% for chlorzoxazone;85.68%±2.81%,93.53%±3.70% and 110.67%±5.54% for midazolam,respectively.Conclusions:The established method is simple,rapid and reliable,and can be suitable for determining the plasma concentrations of probes and evaluating the CYP2E1 and CYP3A4 activities in the rats.