A liquid chromatography-MS-MS turbulent flow on-line extraction method was developed for the determination of trimebutine (TMB) and its main active metabolite N-mono-desmethyltrimebutine (nortrimebutine or nor-TMB) in human plasma. After protein precipitation and internal standard (IS, haloperidol-d4) addition, 50 µL of the supernatant were transferred onto a Cyclone-Turbo-Flow extraction column followed by an Hypersil PFP Gold analytical column. Detection was carried out on a triple quadrupole tandem mass spectrometer using positive electrospray ionization. The transitions used were m/z 388.0→343.0, 374.0→195.0 and 380.1→169.0 for TMB, nor-TMB and IS, respectively. The method was validated over the concentration range of 10-1,000 ng/mL for both compounds. The accuracy evaluated at three concentrations was within 90.0-98.5% and the intra- and interday coefficient of variation's for the two molecules were <8.7%. The method was applied to a toxicokinetic study of a self-poisoning case with TMB in a 19-old girl. The concentration of TMB decreased from 747 to 77 ng/mL, while nor-TMB decreased from 9,745 to 205 ng/mL after 5 days and the fatal issue. This case confirms the literature underlining the potential toxicity of TMB, which has long time been considered as a harmless molecule.
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