Abstract
Objectives: To estimate bioequivalence of two atorvastatin formulations, Lipitor & Orvastin in healthy Pakistani volunteers.
Methodology: It was single dose, randomized, crossover study, which was carried out in 24 healthy male volunteers, who received single dose of 80 mg tablet of test formulation (Orvastin) and same dose of originator product (Lipitor). Blood samples were taken up to 48 hours post dose and concentrations of atorvastatin were determined by HPLC. Progesterone was used as internal standard. Plasma concentration-time curves were prepared to determine the AUC and bioequivalence. Statistical analysis of pharmacokinetic parameters and reference formulation was performed using one compartmental model of software APO, MW PHARM version 3.60. Results: Administration of tablet Lipitor showed a maximum concentration Cmax of atorvastatin 23.97±7.0 µg/l and the time to achieve maximum concentration Tmax was 3.29±0.25 hours, while tablet Orvastin showed a maximum concentration Cmax of atorvastatin 26.69±6.67 µg/l and the time to achieve maximum concentration Tmax was 3.33±0.41 hours. The AUC(0-∞) for tablet Lipitor was 174.28±62.50h/µg/l and for tablet Orvastin, it was 208.74±71.51 h/µg/l. The AUC(0-t) for tablet Lipitor was 175.24±59.28 h/µg/l and for the tablet Orvastin, it was 208.77±67.49 h/µg/l. Conclusion: The two atorvastatin formulations, i.e. test formulation of atorvastatin and reference preparation were bioequivalent in terms of the rate and extent of absorption.

Key words: Atorvastatin, HPLC, statins, bioequivalence study.