Release Characteristics of Nifedipine from 2-Hydroxypropyl-.BETA.-cyclodextrin Complex during Storage and Its Modification of Hybridizing Polyvinylpyrrolidone K-30.

Abstract

Amorphous nifedipine powders were prepared by spray-drying with 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD) or polyvinylpyrrolidone K-30 (PVP). Upon storage of the products at a high temperature and humidity, nifedipine crystallized in matrices, yielding both bigger crystals (>50 μm) in a PVP matrix and smaller crystals (about 5 μm) in a HP-β-CyD matrix. The release of nifedipine from tablets containing the HP-β-CyD complex was accelerated upon storage, whereas that from the PVP solid dispersion was decelerated. The deceleration of the release rate was attributable to the growth of nifedipine crystals with a larger size in the PVP matrix. The release of nifedipine from the HP-β-CyD complex at the early stage of storage was rather slow due to the low wettability and high compressibility of the tablets. However, over a longer period of storage, the inhibitory effect of HP-β-CyD on the crystal growth of nifedipine took effect, leading to the release acceleration. To maintain the improved release of nifedipine over a long period of storage, a possible combination of HP-β-CyD and PVP was investigated to act as a hybridizing drug carrier. Among various compositions, the 1 : 3 : 1 (nifedipine : PVP : HP-β-CyD, weight ratio) product gave the most appropriate release profile without any decreased release of nifedipine at the early and late stages of storage.