Determination of finasteride in human plasma by liquid chromatography–electrospray ionization tandem mass spectrometry with flow rate gradient

ArticleinEuropean Journal of Drug Metabolism and Pharmacokinetics 35(3-4):137-46 · January 2011with9 Reads
Impact Factor: 1.56 · DOI: 10.1007/s13318-010-0013-x · Source: PubMed

    Abstract

    In this study, an attempt was made to describe and validate liquid chromatography–electrospray ionization tandem mass spectrometry as a fast, sensitive and reproducible method for determining finasteride in human plasma. Finasteride and internal standard (pantoprazole) were extracted by liquid–liquid extraction using methyl tert-butyl ether. Separation was performed by using a flow rate gradient on a reverse phase C18 column at 25°C. The mobile phase consisted of methanol–water (70:30, v/v) containing 0.5% anhydrous formic acid. The protonated analytes were quantitated in positive ionization by multiple reaction monitoring in mass spectrometry. The mass transitions are m/z 373.4→305.3 and 384.1→200.0 for finasteride and pantoprazole, respectively. The method had a run time of 3.6 min and a linear calibration curve at a range of 0.2–100 ng mL−1 (r
    2 = 0.9958). The lower limit of quantification was 0.2 ng mL−1. The extraction recoveries of finasteride from the biological matrix were more than 82.7%, and the intra- and inter-day precision of the assay at four concentrations were 2.4–8.0% with an accuracy of 94.3–105.8%. The developed method requires less plasma (0.1 mL), but has high sensitivity. The validated method has been successfully used to analyze human plasma samples in pharmacokinetic or bioequivalence studies.