Development and validation of an LC-MS assay for finasteride and its application to Prostate Cancer Prevention Trial sample analysis

摘要

An analytical method has been developed and validated for the quantitative determination of finasteride, a potent 5 α –reductase inhibitor, in human plasma. Calibration curves are linear in the concentration range of 1 to 100 ng/ml. Sample pretreatment involves a liquid-liquid extraction with ethyl acetate using 0.2 ml aliquots of plasma. Finasteride and the internal standard, beclomethasone, are separated on a Waters Symmetry Shield RP18 column (50 × 2.1 mm, 3.5 μm), and eluted using a gradient mobile phase composed of acetonitrile and 10 mM ammonium acetate with 0.1% formic acid. The column eluant is monitored by mass spectrometry with electrospray ionization. A complete validation of the method has been performed. For quality control samples at three different concentrations that were analyzed in quintuplicate, on six separate occasions, the accuracy and precision range from 95.2 to 101% and 3.4 to 7.3%, respectively. The developed method was subsequently applied to measure the steady state finasteride concentration of patients who participated in the Prostate Cancer Prevention Trial (PCPT).