Simultaneous determination of atorvastatin and its metabolites in human plasma by UPLC-MS/MS

A rapid, sensitive and selective ultra-performance liquid chromatography mass spectrometry (UPLC-MS/MS) method was developed and validated for the quantification of atorvastatin and all its as-yet-identified metabolites in human plasma. Atorvastatin, its metabolites, and the internal standard (IS) were isolated from human plasma by liquid–liquid extraction with ethyl acetate and then separated on an Acquity UPLC HSS T3 column (3.0 mm × 100 mm, 1.8 μm) using 0.05% (v/v) formic acid in water/acetonitrile (25 : 75, v/v) as the mobile phase. Atorvastatin and all five metabolites were eluted within 4 min. Quantification was performed through positive ion electrospray ionization (ESI). The responses of atorvastatin and its metabolites ortho-hydroxy atorvastatin, para-hydroxy atorvastatin, atorvastatin lactone, ortho-hydroxy atorvastatin lactone, and para-hydroxy atorvastatin lactone were optimized at the m/z 559.4 → 440.1, m/z 575.4 → 466.2, m/z 575.5 → 440.5, m/z 541.3 → 448.3, m/z 557.3 → 448.3, and m/z 557.3 → 448.3 transitions, respectively. The assay was validated in the linear range of 0.2–40 ng mL−1 for atorvastatin and its metabolites. The intra- and inter-day precision variations were between 3.3% and 13.9%. The matrix effects of plasma were in the range of 102.7–105.5% for atorvastatin and 90.3–96.6% for atorvastatin lactone. This method was successfully applied in clinical studies of atorvastatin in coronary artery disease patients.