Phase characterization of indomethacin in binary solid dispersions with PVP VA64 or Myrj 52

In the present study the properties of binary solid dispersions made up of PVP VA64, Myrj 52 and indomethacin (IMC) are studied and characterized. The solid dispersions were prepared by dissolving the materials in dichloromethane, followed by solvent evaporation under reduced pressure at 55 °C in a rotavapor. Binary solid dispersions were characterized by standard and modulated temperature differential scanning calorimetry (MTDSC), thermogravimetry (TGA) and X-ray powder diffraction (XRPD). XRPD analysis showed that the initial IMC was in its γ-form, and that it was transformed to the β-form (reported to be a solvate) together with an amorphous fraction in the solid dispersions. A mixture of the β-form and amorphous IMC was also obtained in the binary systems containing less than 30% polymer. IMC without adding polymer was subjected to the same experimental procedures as in the solid dispersions, and used as a model to characterize the solid-state transformations. The following order of transitions was observed: from the initial γ-form, the β-form was obtained together with an amorphous component, then the crystalline β-form transforms into the α-form which melts and recrystallizes into the most stable γ-form.