抄録
The amorphous state of drugs was obtained by the grinding of drugs with cyclodextrins. The dispersed state of the drug molecules in the ground mixtures was investigated by IR spectral analysis using α-, β-, γ-cyclodextrins and linear oligosaccharides. It was suggested that aspirin molecules were included in the cavity of β-, and γ-cyclodextrins by the grinding, while they were not included with α-cyclodextrin.
Solid state aspirin decomposition rates were measured in various aspirin-cyclodextrin systems. The decomposition rates of aspirin were related to the dispersed states of the acetoxyl group of aspirin molecules. When the acetoxyl group was in the free state, the system showed a slow decomposition rate. On the other hand, when it was hydrogen bonded with the hydroxyl group of cyclodextrin, the systems showed greater decomposition rates.
The effects of humidity on the crystallization of the ground mixtures with cyclodextrins were also discussed. Amorphous ground mixtures were changed into crystals when they were stored at a higher relative humidity (RH). The RHs in which the ground mixtures crystallized were correlated with the hydration numbers of the respective inclusion compounds.
