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 (RL) with different drug-to-polymerratios were prepared by a solvent method (coevaporates) and were characterised in the solid state in comparison withthe corresponding physical mixtures. The work was aimed at characterising the interactions occurring between DIFand RS or RL polymers, along with their influence on the in-vitro drug-dissolution pattern. The findings suggest thatthe drug did not change its crystalline form within the polymer network. Drug dispersion in the polymer matrixstrongly influences its dissolution rate, which appears slower and more gradual while increasing the polymer ratios.Moreover, DIF is known to be a photosensitive compound, and its photoproduct has been found to be a toxic agent.This can be evidenced by testing red blood cell membranes for their resistance to the osmotic shock induced by UVAirradiation in the presence of DIF. The presence of some DIF/RS coevaporates was shown to reduce significantly thedrug photosensitization process towards cell membranes. This suggests the possibility of combining the design of adrug delivery system with a photoprotective strategy.