Pharmacokinetics Of Ezetimibe Tablets And Dabigatran Etexilate Capsules

Objective:A liquid chromatography-tandem mass spectrometry（LC-MS/MS）method was developed and validated to simultaneously quantify ezetimibe and its glucuronidated metabolite（ezetimibe glucuronide）in human plasma,and a LC-MS/MS method was developed and validated to quantify dabigatran in human plasma.The method was applied to a pharmacokinetic study in healthy Chinese subjects.Method:Ezetimibe and ezetimibe glucuronide were extracted from plasma by liquid-liquid extraction using methyl tert-butyl ether.A Poroshell 120 SB-C₁₈（2.1×50mm,2.7μm）and mobile phase consisting of acetonitrile and water were used to achieve chromatographic separation.The flow rate was set at 0.4 m L·min^-1.Quantification was conducted using an electrospray ionization source in negative ion mode with multiple reaction monitoring transitions of m/z 408.5→271.3 for ezetimibe,m/z 584.5→271.2for ezetimibe glucuronide and m/z 364.0→188.9 for indapamide（internal standard）.Dabigatran was extracted from plasma by the protein precipitation using acetonitrile.Chromatographic separation was achieved on a Hanbon Hedera ODS-2（2.1×150 mm,5μm）column using mobile phase that consisted of 0.2%formic acid aqueous（containing 2 m M ammonium acetate）and methanol with gradient elution,and the flow rate was set at 0.5 m L·min^-1.Quantification was conducted using an electrospray ionization source in positive ion mode with multiple reaction monitoring transitions of m/z 471.7→289.2 for dabigatran and 397.2→351.2 for benazeprilat（internal standard）.Result:The calibration curve was linear over concentration range of 0.1001-12.01 ng·m L^-1for ezetimibe,0.5000-200.0 ng·m L^-1for ezetimibe glucuronide and1.038-415.2 ng·m L^-1for dabigatran,respectively.The coefficient variation values of inter-and intra-day precision for three analytes were no more than 10.8%,the matrix effect was 98.1%～104.6%、98.9%～102.6%and 95.3%～106.5%,respectively;the extraction recovery was 94.5%～101.1%、97.4%～101.4%and 102.3%～102.6%,respectively,the method could meet the requirements of biological sample analysis.The main pharmacokinetic parameters obtained from the 12 healthy Chinese subjects orally administered of ezetimibe tablets and dabigatran etexilate capsules were shown as follows:C_maxof ezetimibe,ezetimibe glucuronide and dabigatran was 6.456±3.686,91.82±33.10 and 136.1±59.0 m L^-1,respectively;T_maxwas 2.54±2.68,1.38±1.4 and1.75±0.60 h,respectively;t_1/2was 25.5±24.5,18.8±5.8 and 10.6±3.0 h,respectively;AUC_0-twas 123.0±60.9,844.5±642.9 and 1287±694 ng·h·m L^-1,respectively;AUC_0-∞was 145.8±72.9,899.0±646.0 and 1312±699 ng·h·m L^-1,respectively.Conclusion:The analytical methods in the study were accurate and reliable,which were successfully used to analyze ezetimibe,ezetimibe glucuronide and dabigatran in human plasma for application in the pharmacokinetic study.The multiple-peak in the concentration-time curve of ezetimibe is attributed to enterohepatic recirculation.There was significant difference in the systemic exposure(C_maxand AUC)of ezetimibe and ezetimibe glucuronide between healthy Chinese subjects and Caucasians（P<0.05）,the systemic exposure variations may result from body weight and genetic variability of UDP-glucuronosyltransferase 1A1（UGT1A1）and others.There was significant difference in the systemic exposure(C_maxand AUC)of dabigatran between healthy Chinese subjects and Caucasians（P<0.05）,the systemic exposure variations may result from body weight and genetic variability of carboxylesterases 1（CES1）and others.