Determination of a novel selective inhibitor of type 1 5 alpha-reductase in human plasma by liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

摘要

lA sensitive and specific assay of human plasma for the determination of (5 alpha,7 beta,16 beta)-16[(4-chlorophenyl)oxy]-4,7-dimethyl-4-aza-andronstan-3-one (I), a selective inhibitor of human type 1 5 alpha-reductase, has been developed. The method is based on high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS-MS) detection. The analyte (I) and internal standard, Proscar (II), were isolated from the basified biological matrix using a liquid-liquid extraction with methyl-tert.-butyl ether (MTBE). The organic extract was evaporated to dryness, the residue was reconstituted in mobile phase and injected into the HPLC system. The MS-MS detection was performed on a PE Sciex API III Plus tandem mass spectrometer using a heated nebulizer interface. Multiple reaction monitoring using the precursor-->product ion combinations of m/z 430-->114 and 373-->305 was used to quantify I and internal standard (II), respectively. The assay was validated in the concentration range of 0.5 to 500 ng/ml in human plasma. The precision of the assay, expressed as coefficient of variation (C.V.), was less than 7% over the entire concentration range, with adequate assay specificity and accuracy. The HPLC-MS-MS method provided sufficient sensitivity to completely map the 24 h pharmacokinetic time-course following a single 0.5 mg dose of I. (C) 1998 Elsevier Science B.V. All rights reserved. [References: 11]