Aspects of the interactions between indomethacin and nicotinamide in solid dispersions

A series of indomethacin/nicotinamide binary system-melts were prepared as models to study some aspects of the potential physico-chemical interactions between indomethacin and nicotinamide. The comparative analysis of the data from FT-IR- and UV spectroscopy, DSC, X-ray diffractometry and equilibrium solubility study showed that formation of complexes of different stoichiometry can take place in the solid state and in solution. The aqueous solubility of the assumed complexes of drug/carrier molar ratio above 1:1 (M/M) did not exceed the solubility of the pure indomethacin (IND) (treated), which was prepared as the model melts. The melts with a low drug content (e.g. 7.5 and 9.1% melts) were found to be in a metastable physical state probably due to the amorphous nature of the indomethacin or its complex. They can be in situ transformed into 1% indomethacin aqueous solution.