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

• We develop an assay method for mesoridazine in rat plasma using LC–MS/MS.
• We develop a simple, rapid, and sensitive method by simple protein precipitation.
• This assay variability limits set forth in the FDA guidelines.
• The present method can be applied to pharmacokinetic and/or toxicokinetic studies.

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.