Simultaneous quantitation of lovastatin and an active metabolite in Rat Plasma by UPLC-QTRAP-MS/MS and its application in the pharmacokinetic

OBJECTIVE To develop an ultrahigh-pressure liquid chromatography triple-quadrupole linear ion-trap tandem mass spectrometry (UPLC-QTRAP-MS/MS) method for the pharmacokinetic study of lovastatin and its active metabolite (lovastatin acid) in rat plasma. METHODS Plasma samples were extracted by liquid-liquid extraction with ethylacetate, and simvastatin was used as the internal standard (IS). The chromatographic separation was carried out on an Agilent ZORBAX C₁₈(2.1 mm×50 mm, 1.8 μm) column with a gradient mobile phase consisting of acetonitrile and 0.1% formic acid. The flow rate was set at 0.4 mL·min^-1 and the column temperature was 40℃. The detection was performed on positive electrosprayion (ESI⁺) in the multiple reaction monitoring (MRM) mode with transitions of m/z 405.1^®225.1, m/z 423.2^®199.2 and m/z 419.2^®199.1 for lovastatin, lovastatin acid and simvastatin, respectively. RESULTS The method was arranged from 0.08-80.0 ng·mL^-1 and 1.60-1 600.0 ng·mL^-1 for lovastatin and lovastatin acid, respectively. The lower limits of quantification for lovastatin and lovastatin acid were defined as 0.08 ng·mL^-1 and 1.60 ng·mL^-1, respectively. The intra-day and inter-day precision values obtained were <9.0% and the accuracy was between -5.18% and 6.83% for each analyte. The extraction recoveries of their five concentrations for lovastatin and lovastatin acid were all ≥ 72.26%, and the RSD of the extraction recoveries were ≤ 10.83%. The matrix effects ranged from 91.11% to 105.73% and RSD were ≤ 7.46%. The maximum plasma concentrations (C_max) were (136.22±30.25)ng·mL^-1 and (212.57±33.92)ng·mL^-1; the time to maximum plasma concentration (T_max) were (1.58±0.11)h and (2.15±0.26)h; the half-life (t_1/2) were (35.42±12.67)h and (17.86±6.15)h and the areas under the concentration time curves (AUC_0-24h) were (279.92±44.18)ng·h·mL^-1 and (390.34±20.15)ng·h·mL^-1 for lovastatin and lovastatin acid, respectively. CONCLUSION The method is rapid, sensitive and accurate, and it may be applied to the pharmacokinetic study of lovastatin and lovastatin acid in rat plasma.