Liquid Chromatographic-MS/ MS Determination of Atorvastatin and Metabolites in Human Plasma

The aim of the present study was to develop a chromatographic method for the analysis of atorvastatin, Ortho- and Para -hydroxyatorvastatin in human plasma after administration of atorvastatin at the dose of 40 mg in clinical studies. Sample preparation was performed by solid phase extraction and was followed by separation of the analytes on an HPLC system with a linear gradient and a mobile phase consisting of acetonitrile, water and formic acid. Detection was achieved by tandem mass spectrometry operated in the electrospray positive ion mode. Validation of the method for the compounds for which reference compounds were available (acid forms of atorvastatin, o- and p-hydroxyatorvastatin) showed linearity within the concentration range for atorvastatin acid 0.2–40 ng/ml, Para-hydroxyatorvastatin acid 0.250-50 ng/ml, and ortho-Hydroxyatorvastatin acid 0.25–50 ng/ml (r 2 > 0.99, n=3 for all analytes). Accuracy and precision (evaluated at 0.5, 17 and 31 ng/ml for atorvastatin, 0.66, 22, 40 ng/ml for Para--hydroxyatorvastatin and ortho-hydroxyatorvastatin) were both satisfactory. The detection limit was 0.06 ng/ml for atorvastatin and para -hydroxyatorvastatin, and 0.15 ng/ml for ortho -hydroxyatorvastatin. The method has been successfully applied in a clinical study where atorvastatin, o- and para - hydroxyatorvastatin could be detected in a 24-h sampling interval after administration of registered dose of atorvastatin (40 mg) for one week.