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

The synthetic iron oxides are strong absorbers of radiation wavelength s below 400 nm. They also have great hiding power due to their high re fractive indices and high tinctorial capacity. These properties of iro n oxides were utilized in photostabilization of two light-sensitive dr ugs, sorivudine (BV-araU) and nifedipine. Light stability studies on 1 0 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 40 0 foot candle intensity. Subsequent to exposure, they were assayed for loss in potency and increase in level of degradants due to photodecom position. Uncoated tablets containing 0.2% w/w yellow iron oxide were found to be more light stable than those without it. The effect of inc orporation of 0.2% w/w yellow iron oxide in the tablet core on photoly tic degradation was also compared with that of a film coated tablet. I nclusion of 0.2% w/w yellow, red, or black iron oxide into uncoated ta blets 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 lig ht protection than the inclusion of either 0.2% w/w yellow or red iron oxide alone.