PHOTOSTABILIZATION OF UNCOATED TABLETS OF SORIVUDINE AND NIFEDIPINE BY INCORPORATION OF SYNTHETIC IRON-OXIDES

The synthetic iron oxides are strong absorbers of radiation wavelengths below 400 nm. They also have great hiding power due to their high refractive indices and high tinctorial capacity. These properties of iron oxides were utilized in photostabilization of two light-sensitive drugs, sorivudine (BV-araU) and nifedipine. Light stability studies on 10 mg potency aqueous wet granulated uncoated tablets of sorivudine and nifedipine formulated with or without 0.2% w/w yellow iron oxide were performed by exposing them directly to room light and/ or light of 400 foot candle intensity. Subsequent to exposure, they were assayed for loss in potency and increase in level of degradants due to photodecomposition. Uncoated tablets containing 0.2% w/w yellow iron oxide were found to be more light stable than those without it. The effect of incorporation of 0.2% w/w yellow iron oxide in the tablet core on photolytic degradation was also compared with that of a film coated tablet. Inclusion of 0.2% w/w yellow, red, or black iron oxide into uncoated tablets provided more light protection than 11% w/w coating with Opadry(R) white. Furthermore, inclusion of a combination of 0.05% w/w red and 0.04% w/w yellow iron oxides into uncoated tablets gave them more light protection than the inclusion of either 0.2% w/w yellow or red iron oxide alone.