Properties of felodipine-poly(vinylpyrrolidone) solid dispersion films and the impact of solvents

Abstract

Solid dispersions of felodipine in polyvinylpyrrolidone (PVP) K90 films were prepared by a solvent evaporation method using various volume ratios of dichloromethane (DM) and ethanol (E). Compared to the others, the solubility parameter of the binary mixtures of DM/E at 5/5 was most close to the solubility parameter of PVP. DSC analysis revealed a single glass transition temperature (Tg) of the felodipine/PVP films, suggesting that felodipine and PVP were miscible. As indicated by DSC and dynamic mechanical analysis, the T g of the felodipine/PVP film prepared by using a DM/E of 5/5 was higher than those prepared using other DM/E ratios. This high Tg could reflect the high rigidity of this felodipine/PVP film and a high interaction between felodipine and PVP. Using this DM/E ratio, which is a good solvent for this system, the PVP chain elongation could be promoted and provided for a better interaction with felodipine. This strong interaction accounts for the felodipine/PVP film rigidity. Furthermore, according to the texture analysis, the felodipine/PVP film prepared by a DM/E of 5/5 gave the highest Young's modulus and indicated a high polymer chain rigidity. FTIR indicated an interaction of PVP and felodipine. According to the PXRD, all felodipine/PVP films were in the amorphous state and this amorphous state remained for more than 2 months. Thus a film prepared by a DM/E of 5/5 showed the highest stability of its amorphous state after being kept for 2 months.