Finasteride in biological fluids: extraction and separation by a graphitized carbon black cartridge and quantification by high-performance liquid chromatography.

A simple, specific and sensitive high-performance liquid chromatographic method has been developed and validated for the determination of finasteride in human plasma. A solid-phase extraction procedure was used to isolate finasteride from the biological matrix before quantitative analysis. The analyte was separated on a Symmetry reversed-phase column using acetonitrile-0.04 M orthophosphoric acid (pH 4.0) as mobile phase and quantified by measuring its UV absorbance at 215 nm. The limit of detection for the analyte was 0.005 microg/ml. 4-Androstene-3,17-dione was used as internal standard. The calibration graph of the method was linear from 0.01 to 3.0 microg/ml of finasteride in human plasma, and the coefficient of variation less than 4.5%. This HPLC procedure is simple, precise and accurate for the determination of finasteride in human plasma.