ObjectiveTo establish a HPLCMS method for determinating the concentration of 4panisamidobutyric acid(ABA),the main active metabolite of aniracetam capsules in the plasma, and to compare the bioequivalence of two aniracetam capsules in healthy volunteers.Methods Twentyfour healthy male volunteers were randomly given an oral single dose of 200 mg test or reference aniracetam capsules in a crossover manner. The concentrations of ABA were assayed by HPLCMS at different time points. The main pharmacokinetic parameters and the relative bioavailability of two preparations were calculated, and their bioequivalence was evaluated．ResultsThe pharmacokinetic parameters of test and reference preparations were as fol1ows: Cmax being (9.30±5.13) and (8.70±3.17) μg/ml; t max being (38.41±17.89) and (39.09±19.92) min; t 1/2 being (37.21±10.51) and (38.45±9.24 ) min; AUC0t being (555.21±157.10) and (545.39±97.22) μg/(ml·min), and AUC0∞ being (566.24±158.01) and (554.71±100.32) μg/(ml·min), respectively. Relative bioavailability F0t and F0∞ values of the test preparation were (101.22±17.17)% and (101.52±16.63)%, respectively. No significant differences were found in the main pharmacokinetic parameters between the two preparations. ConclusionThe two aniracetam preparations tested in the present study are