Development and validation of atorvastatin by LC-ESI-MS and application in bioequivalence research in healthy Chinese volunteers

The aim of this research was to develop a sensitive liquid chromatographic-electrospray ionization-mass spectrometric (LC-MS) method for direct measurement of the concentration of Atorvastatin in human plasma. Plasma samples (1 mL) were extracted with 3 mL ethyl acetate, and by a simple reversed-phase chromatography. Pitavastatin was used as internal standard (IS). The LOQ was 0.25 ng mL^-1 (RSD 4.24%). The assay was linear from 0.25-20 ng mL^-1. And the correlation coefficient for the calibration regression line was 0.9996 or better. Intra-day and inter-day accuracy were better than 15%. The method has been successfully used for a pharmacokinetic study with human subjects. A two-period crossover designed bioequivalence research was also progressed in healthy Chinese volunteers. Among the pharmacokinetic data obtained, T _max was 1.36 ± 0.68 h for reference formulation and 0.81 ± 0.54 h for test formulation. C _max was 8.54 ± 5.06 ng mL^-1 for reference formulation and 9.54 ± 3.68 ng mL^-1 for test formulation. t _1/2 was 8.50 ± 2.74 h for reference formulation and 9.24 ± 3.17 h for test formulation. AUC _0-48h was 54.77 ± 21.82 h ng mL^-1 for reference formulation and 55.66 ± 20.91 h ng mL^-1 for test formulation. The method was successfully applied to the study of pharmacokinetics of Atorvastatin in healthy Chinese volunteers.