Determination of levamlodipine concentration by LC-MS/MS and its chiral transformation potential in human plasma

Abstract

Objective To determine S-(-)-amlodipine level in human plasma by LC-MS/MS method,and to investigate its chiral transformation potential in healthy male volunteers.Methods The 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.Results The 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.Conclusion The present method is highly selective,sensitive,accurate and with no endogenous interference for pharmacokinetic study.R-(+)-amlodipine is not found in the plasma,indicating that there is no chiral transformation in healthy male volunteers.