Preparation, characterisation and photosensitivity studies of solid dispersions of diflunisal and Eudragit RS100 (R) and RL100 (R)

Solid dispersions of diflunisal (DIF) with Eudragit RS100 (RS) and RL100 (R L) with different drug-to-polymer ratios were prepared by a solvent method (coevaporates) and were characterised in the solid state in comparison with the corresponding physical mixtures. The work was aimed at characterising the interactions occurring between DIF and RS or RL polymers, along with th eir influence on the in-vitro drug-dissolution pattern. The findings sugges t that the drug did not change its crystalline form within the polymer netw ork. Drug dispersion in the polymer matrix strongly influences its dissolut ion rate, which appears slower and more gradual while increasing the polyme r ratios. Moreover, DIF is known to be a photosensitive compound, and its p hotoproduct has been found to be a toxic agent. This can be evidenced by te sting red blood cell membranes for their resistance to the osmotic shock in duced by UVA irradiation in the presence of DIF. The presence of some DIF/R S coevaporates was shown to reduce significantly the drug photosensitizatio n process towards cell membranes. This suggests the possibility of combinin g the design of a drug delivery system with a photoprotective strategy. (C) 2001 Elsevier Science B.V. All rights reserved.