Abstract: AimTo develop an HPLC-ESI-MS assay for determination of trimebutine in human plasma and to investigate the pharmacokinetics and bioequivalence of two trimebutine tablets in human. MethodsAfter being made alkaline with saturated sodium bicarbonate, plasma was extracted by cyclohexane and separated by HPLC on a reversed-phase C₁₈ column with a mobile phase of 10 mmol·L^-1 ammonium acetate buffer solution (pH 3.5)-methanol (18∶82). HPLC-ESI-MS was performed in the selected ion monitoring (SIM) mode using target ions at _m/z 388 for trimebutine and _m/z 280 for the internal standard (sibutramine, IS). The fragmentor voltage was 50 V. A randomized cross-over design was performed in 20 healthy volunteers. In the two study periods, a single 100 mg dose of each tablet was administered to each volunteer. ResultsCalibration curve was linear over the range of 0.3-150 μg·L^-1. The main pharmacokinetic parameters of t_1/2, t_max and C_max were (9.2±2.8) h, (1.0±0.3) h and (40±20) μg·L^-1 for the reference tablet; (9.2±2.3) h, (0.9±0.4) h and (41±20) μg·L^-1 for the test tablet. The relative bioavalability of the test tablet was (97±13)%. The results of variance analysis and two one-sided t-test showed that there was no significant difference between the two formulations in the AUC and C_max. ConclusionThe assay was proved to be sensitive, accurate and convenient. The two formulations were bioequivalent.