Effects of wet-granulation process parameters on the dissolution and physical stability of a solid dispersion

This study investigated how the process parameters of wet-granulation affect the properties of solid dispersions (SDs), such as dissolution and physical stability. SDs of nilvadipine (NIL) and hypromellose prepared by spray-drying were wet-granulated and dried under various conditions. The NIL concentration at 4h and area under the curve from dissolution tests were taken to indicate dissolution. Then, the NIL crystallinity calculated from powder X-ray diffraction patterns of SD granules stored at 60°C for 3 months was evaluated to indicate physical stability. A statistical analysis revealed that the amount of granulation liquid (w/w%) and the ratio of water to ethanol in the liquid (v/v%) significantly affected the dissolution property, and that the drying temperature had a significant effect on the physical stability. Although exposure to water makes the wet-granulation process seem less suitable for granulating a SD, the results indicated that the process can be used to develop SD granules by selecting appropriate conditions, such as a lower proportion of granulation liquid, a higher water to ethanol ratio in the liquid, and a higher drying temperature.