A novel gradient LC-MS/MS method for simultaneous determination of trimebutine maleate and its two metabolites in human plasma

A simple and rapid chromatography-tandem mass (LC-MS/MS) method has been developed for simultaneous determination of trimebutine maleate (TM) and its two major metabolites N-didemethyltrimebutine (APB) and 3, 4, 5-trimethoxybenzoic acid (TMBA) in human plasma. Trimebutine maleate and its metabolites were analyzed by protein precipitation followed by reverse-phase HPLC separation on a Sun Fire C-18 column. An 5 min gradient elution of mobile phase was used to obtain quality chromatography. The API4000 mass spectrometer was operated in positive-negative switching ionization mode. Positive ionization was applied to detect TM, APB and BP (IS-1, positive internal standard) in the first 3.4 min. After an interval of 0.1 min, the instrument was automatically converted to negative ionization mode to detect TMBA and TOBA (IS-2, negative internal standard). The method was validated over the concentration range of 0.5-500 ng/mL for trimebutine maleate and APB, 50-50000 ng/mL for TMBA. Inter-and intra-day precision (RSD%) for trimebutine maleate and its metabolites were all within 15% and the accuracy was within 85-115%. The mean recoveries were 102.4% for TM, 100.9% for APB and 92.7% for TMBA. The method was applied to a pharmacokinetic study of trimebutine maleate and its metabolites in healthy Chinese volunteers.