ObjectiveTo determine S-(-)-amlodipine level in human plasma by LC-MS/MS method, and to investigate its chiral transformation potential in healthy male volunteers. MethodsThe separation of amlodipine was performed by CHIRAL-AGP analytical column (150.0 mm×4.0 mm, 5 μm) with 10 mmol/L acetate buffer (pH 4.38)-2-propanol (982, V/V) as the mobile phase and chlordiazepoxide as the internal standard. The plasma S-(-)-amlodipine was extracted with solid phase extraction in ten healthy male volunteers at different time points after oral test (2.5 mg). Atmospheric-pressure chemical ionization (APCI) and multiple reaction monitoring (MRM) were used with positive ion scans, and the mass transition pairs of m/z 409.0→237.9 and m/z 300.0→282.0 were used to detect amlodipine and internal standard, respectively. ResultsThe linear calibration curve of each enantiomer of amlodipine showed excellent correlation over the range of 0.1031 μg/L (20.62 μg/L(r=0.999 8, r=0.999 7). The absolute recovery was more than 70.0%, the relative recoveries were 85.0%-115.0%, and intra-run and inter-run relative standard deviation (RSD) were less than 15.0%. No R-(-)-amlodipine was detected in the plasma of ten healthy male volunteers at different time points after single oral test. The main pharmacokinetic parameters of S-(-)-amlodipine in healthy male volunteers were as follows:t1/2 was (42.77±8.08) h, Cmax was (3.06±0.51) μg/L, tmax was (6.3±1.0) h, MRT was (69.25±8.04) h, AUC0-144 was (176.20±31.89) h·μg·L-1, and AUC0-∞ was (197.92±37.54) h·μg·L-1. ConclusionThe present method is highly selective, sensitive, accurate and with no endogenous interference forpharmacokinetic study. R-(+)-amlodipine is not found in the plasma, indicating that there is no chiral transformation in healthy male volunteers.