Development of Controlled-Release Solid Dispersion Granules Containing a Poorly Water-Soluble Drug, Porous Calcium Silicate, and the Water-Soluble Polymer Polyvinylpyrrolidone

Objectives: This study sought to develop controlled-release solid dispersion granules containing a poorly water-soluble drug, porous calcium silicate (PCS), and a water-soluble polymer. Methods: Nifedipine (NIF) and indomethacin (IND), and several water-soluble polymers were selected to prepare solid dispersion granules. Differential scanning calorimetry, Powder X-ray diffraction, and Fourier transform infrared (FT-IR) were used to estimate the crystallinity of drugs in the PCS granules and to determine interactions between drug and PCS. Results: Among the water-soluble polymers used in this study, only polyvinylpyrrolidone (PVP) permitted sustained release from the NIF granules. The release rates of NIF from the granules decreased as the molecular weight or amount of PVP in the granules was increased. A significant loss of crystallinity of NIF in the granules and the existence of a hydrogen bond between NIF and PCS or PVP, as well as between PCS and PVP were observed. To examine the applicability of this system to other drugs, indomethacin (IND) was selected. However, IND was rapidly released from the PVP-containing granules. FT-IR spectroscopy results revealed the existence of a hydrogen bond between IND and PVP, but IND and PCS appeared to interact via salt formation. Conclusion: Hydrogen bonding among the drugs, PCS, and PVP may have contributed to the slow drug release in the developed system.