LC-ESI-MS/MS method for Quantitation of Lovastatin in Rat Plasma and Liver Homogenate: Application to Pharmacokinetic Study

A sensitive method, using high-performance liquid chromatography-electrospray tandem mass spectrometry was developed for the determination of a hydrophilic liver-specific inhibitor of the enzyme 3-hydroxy-3-methylglutaryl coenzyme-A reductase, lovastatin in rat plasma and rat liver homogenate. Simvastatin was used as an internal standard. In this method, samples were prepared in simple two-step liquid-liquid extraction with ethyl acetate. Isocratic chromatographic separation of reconstituted samples was done with mixture of 10 mM ammonium acetate buffer (pH 4): methanol (10:90,v/v) using Phenomenex ultra sphere guard (RP-18), 30x4.6mm, 5μm column. The detection was performed using API 4000 LC-MS/MS system (Applied Biosystem, MDS Sciex, USA) operated in ESI positive mode. The analysis was performed by multiple reactions monitoring mode. The calibration curve obtained were linear (r2≥0.99) over the concentration range of 0.19–100 ng/mL for both plasma and liver homogenate. The LOD and LOQ for lovastatin were found to be 0.04 ng/mL and 0.19 ng/mL respectively. Lovastatin was found to be stable in plasma, liver homogenate and the reconstituted solution. The method is sensitive and reliable with a total run time of less than 2 min. The developed assay method was successfully applied for the determination of lovastatin in plasma sample collected in the pharmacokinetic study.