Objective: The objective of this study was to compare the in vitro and in vivo characteristics of 2 nifedipine modified-release tablet formulations for once-daily dosing marketed in the European community, which were expected to be bioequivalent.
Methods: In vitro dissolution was tested at different pH values prior to the clinical part of the study. Either 1 tablet of a test formulation or of the reference formulation, both containing 30 mg nifedipine, were administered to healthy white male volunteers immediately after a high-fat breakfast in a randomized, open-label, 2-period crossover design. Plasma samples obtained over the subsequent period of 48 hours were analyzed using a validated LC-MS/MS method. Safety profile and tolerability of the study medications were assessed by analysis of adverse events obtained by vital sign measurements, electrocardiography, and clinical laboratory analysis.
Results: Twelve volunteers were enrolled (median age, 28.0 years [range, 21-42 years]; mean body mass index, 24.2 kg/m(2) [range, 19.3-27.0 kg/m(2)]). In vitro dissolution experiments revealed a significant pH dependency in drug release from the investigational tablets, while the reference tablets were found to have pH-independent dissolution. After oral administration of both tablet formulations in the fed state, marked differences in rate and extent of bioavailability were observed. Geometric mean of AUC(0-last)(test, 504.21 h x ng/mL; reference, 361.28 h x ng/mL) was significantly higher for the test product, with a point estimate of 140% and a corresponding 90% CI of 121% to 161%. For the comparison of Cmax values, geometric means were: test, 76.46 ng/mL; reference, 19.20 ng/mL, with a point estimate of 398% and a CI of 316% to 503%. Thus, a significant difference in rate and extent of bioavailability was observed between the 2 products.
Conclusions: Although both treatments were well tolerated by all volunteers, the test and reference tablets were found to have different pharmacokinetic properties when administered after a high-fat meal.