Quantitative determination of trimebutine maleate and its three metabolites in human plasma by liquid chromatography-tandem mass spectrometry

A sensitive and selective HPLC–MS–MS method was developed for the determination of trimebutine maleate (TM) and its major metabolites N-monodemethyltrimebutine (TM-MPB), N-didemethyltrimebutine (APB) and 3,4,5-trimethoxybenzoic acid (TMBA) in human plasma. The analytes were extracted from plasma samples by liquid–liquid extraction and chromatographed on a YMC J’sphere C18 column. The mobile phase consisted of 2 mM ammonium acetate buffer (pH 6.5)–methanol (20:80, v/v), and at a flow-rate of 0.2 ml/min. Detection was carried out on a triple quadrupole tandem mass spectrometer in multiple reactions monitoring (MRM) mode using positive–negative switching electrospray ionization (ESI). The method was validated over the concentration range of 1–100 ng/ml for trimebutine maleate and APB, 1–500 ng/ml for MPB, and 50–10 000 ng/ml for TMBA. Inter- and intra-day precision (RSD%) for trimebutine maleate and its three metabolites were all within ±15% and the accuracy was within 85–115%. The limit of quantitation was 1 ng/ml for trimebutine maleate, TM-MPB and APB, and 50 ng/ml for TMBA. The extraction recovery was on average 58.2% for trimebutine maleate, 69.6% for MPB, 51.2% for APB and 62.5% for TMBA. The method was applied to the pharmacokinetic study of trimebutine maleate and its metabolites in healthy Chinese volunteers.