Abstract: AimTo develop a HPLC-ESI-MS assay for determination of eperisone hydrochloride in human plasma and investigate the pharmacokinetics and bioequivalence of two eperisone hydrochloride tablets in human. MethodsBuflomedil hydrochloride was used as the internal standard. After alkalized with saturated sodium bicarbonate solution, plasma was extracted with diethylether-cyclohexane (1∶1) and separated using HPLC on a reversed-phase C₁₈ column with a mobile phase of 10 mmol·L_-1 ammonium acetate buffer solution (adjusted to pH 3.88 with acetic acid)-methanol (20∶80). HPLC-ESI-MS was performed in the selected ion monitoring (SIM) mode using target ions at m/z 260 for eperisone and m/z 308 for the internal standard. A randomized crossover 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 0.02-20 μg·L_-1. The limit of quantification for eperisone hydrochloride in plasma was 0.02 μg·L_-1. The main pharmacokinetics parameters T_1/2, T_max and C_max were (2.7±0.4) h, (1.1±0.5) h and (2.8±2.8) μg·L_-1 for the reference tablet; (2.8±0.5) h, (1.1±0.4) h and (3±4) μg·L_-1 for the test tablet, respectively. The relative bioavalability of the test tablet was (101±13)%. ConclusionThe assay was proved to be sensitive, accurate and convenient. The two formulations were bioequivalent.