A sustained release nifedipine fine granules, Sepamit R Granules^® (SP-RG), is a product prepared by using the technique of solid dispersion. Dissolution behavior of nifedipine from SP-RG was tested based on the results of incompatibility. The photostability of SP-RG was also tested. Dissolution rate of nifedipine from SP-RG was 12.5% in JP XII 1st disintegration test fluid (pH 1.2) and 100.9% in JP XII 2nd disintegration test fluid (pH 6.8). Dissolution of nifedipine in JP XII 2nd fluid was delayed by moisture absorption during storage (relative humidity of 75% at 20° for 30 days). Dissolution of nifedipine from SP-RG in JP XII 1st fluid was increased by mixing of SP-RG with sodium bicarbonate or heavy magnesium oxide during storage (relative humidity of 75% at 20° for 30 days).
Nifedipine in SP-RG packaged with polyethylene cellophan laminate paper completely decomposed after 72 hours, under exposure to light (500 lux), while it was stable even after 30 days with aluminium polyethylene laminate paper.