A validated RP-HPLC method to investigate finasteride in human skin after in vitro topically applying vesicular...

The pharmacotherapeutic efficiency of topical drug delivery systems is mainly dominated by the skin distribution of therapeutic agents. In this work, a sensitive, rapid and fully-validated reversed-phase high performance liquid chromatography (RP-HPLC) method was developed to determine finasteride in human cadaver skin after different vesicular formulations were applied. Drug in different depth of skin layers were measured with an EclipseXDB-C18 column. The mobile phase consisted of 75% (v/v) methanol containing 0.2% phosphoric acid buffered to pH 3.0 with triethylamine under isocratic conditions. The system was operated at 40°C and the mobile phase flow rate was set at 1 mL/min. The standard-calibration curve was linear within range of 5 to 200 ng/ml with correlation coefficient 0.9996. The intra-assay precision was less than 3.9% while the inter-assay precision was less than 7.1% with the bias range of -8.6 to 4.1%. This method was found to be specific, accurate, and sensitive and was successfully used to determine the accumulation of finasteride after in-vitro percutaneous delivery by liposomal or ethosomal drug delivery nanocarriers.