Abstract: Aim: The objective was to compare the rate and extent of absorption of three generic formulations with that of a reference formulation when administered in equal doses. Methods: The study design was a singledose, randomized four-way crossover with a 1-week washout period between each phase of the experiment dosing. Plasma concentration-time profiles were determined and the bioavailability of different formulations of nimodipine tablets (A, B, C and D) following oral administration of a 120 mg nimodipine single dose was compared. Results: The Tmax of the tablet A, B, C and D was 0.6±0.2 h,1.1±1.2 h,0.5±0.1 h and 0.5±0.2 h, respectively, the Cmax was 108.8±59.5 ng·ml^-1, 56.1±30.7 ng·ml^-1, 73.2±34.9 ng·ml^-1 and 94.7±41.1 ng.ml^-1, respectively; and the AUC was 175.4±77.9 ng·h·ml^-1, 135.8±62.4 ng.h.ml^-1, 154.8±69.5 ng.h.ml^-1 and 154.5±51.6ng·h·ml^-1, respectively. The relative bioavailabilities of tablets B, C and D compared with tablet A were 83.7%, 93.1% and 97.6%, respectively. The 90% confidence interval for the AUC shown for tablets B and C were 66.7-88.8% and 77.2-102.7%, respectively, less than 80% compared to the reference at the low-range estimate, tablet D was 80.5-107. 1%, greater than 80% compared to the reference at the low-range estimate. Conclusion: The 90% confidence interval with respect to AUC was between 80% and 125%, the formulations B and C were not considered bioequivalent, formulation D was considered bioequivalent compared with formulation A.

Key words: Nimodipine, Nimodipine, High performance liquid chromatography, High performance liquid chromatography, Bioavailability, Bioavailability, Bioequivalence, Bioequivalence