The pharmacokinetics and relative bioavailability/bioequivalence of two formulations of mosapride citrate (CAS 112885-42-4) were assessed in this study. The study was conducted in 20 healthy Chinese male volunteers according to an open, randomized, single-blind, 2-way crossover study design with a wash-out phase of 7 days. Blood samples for pharmacokinetic profiling were taken up to 12 h post-dose, and mosapride citrate plasma concentrations were determined by a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Based on the plasma concentration-time data of each individual during two periods, pharmacokinetic parameters, Cmax, AUCo-t,, AUCo-infinity, and t1/2, were calculated by applying non-compartmental analysis. Pharmacokinetic data for test and reference formulations were analyzed statistically to test for bioequivalence of the two formulations. After oral administration, the values of Cmax, Tmax, t1/2, AUCo-t, AUCo-infinity for test and reference formulations were 68.48 +/- 22.95 and 70.69 +/- 23.78 ng/mL, 0.46 +/- 0.20 and 0.49 +/- 0.21 h, 2.30 +/- 0.30 and 2.24 +/- 0.28 h, 161.17 +/- 52.75 and 171.37 +/- 59.02 ng x h/mL, 165.76 +/- 54.34 and 175.77 +/- 60.54 ng x h/mL, respectively. Both primary target parameters, AUCo-infinity and AUCo-t, were tested parametrically by analysis of variance (ANOVA). Relative bioavailabilities were 95.3 +/- 11.3% for AUCo-infinity and 95.2 +/- 11.3% for AUo-t. Bioequivalence between test and reference formulations was demonstrated for both parameters, AUJCo-infinity and AUCo-t. The 90% confidence intervals of the T/R-ratios of logarithmically transformed data were in the generally accepted range of 80-125%. That means that the test formulation is bioequivalent to the reference formulation of mosapride citrate.