In-vivo and in-vitro evaluations of a modified-release oral dosage form of nifedipine by hybridization of hydroxypropyl-beta-cyclodextrin and hydroxypropylcelluloses in dogs.

To maintain a suitable blood level of nifedipine for a long period of time, double-layer tablets consisting of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) and 3% nonionic surfactant (HCO-60) as a fast-release portion and hydroxypropylcelluloses (HPCs) with different viscosity grades (low, medium and high) as a slow-release portion were prepared, and their in-vitro and in-vivo release behaviours were investigated. Among the seven formulations, the tablet having the mean dissolution time of 0.8-1.3 h gave prolonged plasma nifedipine levels without decrease of AUC after oral administration to dogs. Consequently, the double-layer tablet consisting of HP-beta-CyD with 3% HCO-60/(HPC-low:HPC-medium) in a weight ratio 1/(1.5:1.5) was selected as an appropriate modified-release formulation because it elicited almost comparable retarding effects with superior oral bioavailability compared with those of a commercially available slow-release nifedipine product.