Ds. Desai et al., PHOTOSTABILIZATION OF UNCOATED TABLETS OF SORIVUDINE AND NIFEDIPINE BY INCORPORATION OF SYNTHETIC IRON-OXIDES, International journal of pharmaceutics, 103(1), 1994, pp. 69-76
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.