A simple and rapid LC-MS/MS method for the determination of Enalapril in human plasma for pharmacokinetic and bioequivalence studies in korean healthy volunteers under fasting conditions

Abstract

A simple and rapid liquid chromatography-tandem mass spectrometry method for Enalapril in human plasma was developed and applied to pharmacokinetic and bioequivalence test for 2 formulations of Enalapril (10 mg) capsules in healthy korean volunteers under fasting state. The analytes were extracted from plasma by simple protein precipitation by acetonitrile, separated on YMC C8 column using methanol-10 mM ammonium formate (80: 20, v/v) as the mobile phase, and detected by tandem mass spectrometry with Turbo IonSpray interface operating in the positive ion mode for Enalapril and Glibenclamide (IS) in MRM mode. The ionization was optimized using electro-spray ionization (ESI) (+) and selectivity was achieved by MS/MS analysis, m/z 376.447 -˃ 234.1 for Enalapril and m/z 494.1 -˃ 369.1 for IS. The assay exhibited good linearity in the concentration ranges of 1.0 similar to 300 ng/mL for Enalapril in human plasma with lower limit of quantification (LLOQ) of 1.0 ng/mL. The chromatographic run time was approximately 2.0 min. No endogenous compounds were found to interfere with the analysis. The accuracy and precision were acceptable for concentrations over the standard ranges. The method was successfully applied to pharmacokinetic (PK) and bioequivalence (BE) studies by determination of Enalapril in the blood sample taken up to 12 h after oral administration of two Enalapril (10 mg) formulations and results from PK analysis suggested that the 2 types of 10 mg Enalapril tablets should be considered to be bioequivalent for both the extent and rate of absorption in normal volunteers.