Determination of mesoridazine by liquid chromatography–tandem mass spectrometry and its application to pharmacokinetic study in rats

The object of the present study was to develop and validate an assay method of mesoridazine in rat plasma using liquid chromatography-tandem mass spectrometry (LC–MS/MS). Plasma samples from rats were prepared by simple protein precipitation and injected onto the LC–MS/MS system for quantification. Mesoridazine and chlorpromazine as an internal standard (IS) were separated by a reversed phase C18 column. A mobile phase was composed of 10 mM ammonium formate in water and acetonitrile (ACN) (v/v) by a linear gradient system, increasing the percentage of ACN from 2% at 0.4 min to 98% at 2.5 min with 4 min total run time. The ion transitions monitored in positive-ion mode [M + H]+ of multiple-reaction monitoring (MRM) were m/z 387 > 126 for mesoridazine and m/z 319 > 86 for IS. The detector response was specific and linear for mesoridazine at concentrations within the range 0.001–4 μg/ml and the correlation coefficient (R2) was greater than 0.999 and the signal-to-noise ratios for the samples were ≥10. The intra- and inter-day precision and accuracy of the method were determined to be within the acceptance criteria for assay validation guidelines. The matrix effects were approximately 101 and 99.5% from rat plasma for mesoridazine and chlorpromazine, respectively. Mesoridazine was stable under various processing and/or handling conditions. Mesoridazine concentrations were readily measured in rat plasma samples after intravenous and oral administration. This assay method can be practically useful to the pharmacokinetic and/or toxicokinetic studies of mesoridazine.