Development and Validation of an LC-MS-MS Method for the Simultaneous Determination of Simvastatin, Simvastatin Acid and Ezetimibe in Human Plasma and Its Application to Pharmacokinetic Study in the Indian Population.

Abstract

A simple, selective, sensitive and high-throughput liquid chromatography-tandem mass spectrometry (LC-MS-MS) method has been developed and validated for the simultaneous quantification of simvastatin (SS), simvastatin acid (SSA, active metabolite of SS) and ezetimibe (EZM) in K2 EDTA containing human plasma, using simvastatin D6, simvastatin acid D3 and ezetimibe D4 as internal standards (ISTDs), respectively. A volume of plasma sample of only 400 µL was processed by the solid phase extraction technique; then 20 µL of processed sample was run on a Phenomenex, Kinetix XB C18, 150 × 4.6 mm, 5 µm column using an isocratic mobile phase consisting of 10 mM ammonium formate buffer (pH 4.0 ± 0.3): acetonitrile (27 : 73, v/v) with a run time of 6.3 min. The precursor and product ions of SSA, EZM and their ISTDs were monitored on a triple quadrupole instrument operated in the negative ionization mode, and SS was monitored in the positive mode. The method was validated over a concentration range of 0.2-80 ng/mL for SS, 0.1-60 ng/mL for SSA and 0.05-15 ng/mL for EZM. The method has been successfully applied in clinical pharmacokinetic study in the Indian population. The Cmax, AUC0-inf and Tmax values obtained in our study were 10.61 ± 5.287, 77.58 ± 29.367 and 1.62 ± 0.436 for EZM; 69.74 ± 45.274, 190.71 ± 107.271 and 1.74 ± 0.480 for SS; and 25.36 ± 23.576, 139.24 ± 131.653 and 3.95 ± 0.671 for SSA, respectively.