RESUMEN
Investigating the interaction between Diclofenac and Chitosan and its effect on the dissolution in water and in Phosphate buffer system was the objective of this study. Complex formation was attempted between diclofenac and chitosan utilizing optimal condition for their simultaneous ionization in solution form. A co-precipitate was obtained upon mixing the drug and polymer solutions and the co-precipitate was characterized for drug content, differential scanning calorimetiy [DSC], X-ray diffraction and infrared spectroscopy [FTIR] analysis in comparison to diclofenac sodium, diclofenac free acid and their physical mixtures with chitosan. The overall evidence of these comparisons indicated that a physical co-precipitation of chitosan and diclofenac acid was formed with no electrostatic complexation. Having diclofenac acid as a reference for comparison was the key for this conclusion, and comparing the results of the precipitate to only those of diclofenac sodium would have led to false conclusions. The no complexation between the drug and polymer could not be explained based on lack of ionization of either molecule and was explained based on the instability of the complex