Simultaneous determination of ezetimibe and simvastatin in rat plasma by stable-isotope dilution LC-ESI-MS/MS and its application to a pharmacokinetic study

摘要

A simple,sensitive and specilic liquid ehromatography-tandem mass spectrometry method was developed for simultaneous quantification of ezetimibe and simvastatin in rat plasma.The deuterium isotopes:ezetimibe d_4 and simvastatin d_6 were used as internal standards for ezetimibe and simvastatin,respectively.MS/MS detection involved a switch of electron spray ionization mode from negative to positive at retention time 3.01 min.Samples were extracted from plasma by liquid-liquid extraction using tertiary butyl methyl ether.Chromatographic separation was achieved with Agilent Eclipse XBD-C_(18) column using mobile phase that consisted of a mixture of ammonium acetate(pH4.5:10 mM)-acetonilrile(25:75 v/v).The method was linear and validated over the concentration range of 0.2-40.0 ng/mL for simvastatin and 0.05-15.0 ng/mL for ezetimibe.The transitions selected were mlz 408.3→271.1 and mlz 4I2.0→ 275.10 for ezetimibe and ezetimibe d_4.and mlz 419.30→ 285.20 and mlz 425.40 →199.20 for simvastatin and simvastatin d_6.Intra- and inter-batch precisions for ezetimibe were 1.6-14.8%and 2.1-13.4%;and for simvastatin 0.94-9.56%and0.79-12%.respectively.The proposed method was sensitive,selective,precise and accurate for the quantification of ezetimibe and simvastatin simultaneously in rat plasma.The method was successfully applied to a pharmacokinetic study by oral co-administration of ezetimibe and simvastatin in SD rats.