The saturation solubility of PVP:PZQ physical mixtures (PMs) and solid dispersions (SDs) prepared from
ethanol (E/E) or ethanol/water (E/W) by the solvent evaporation method at 1:1, 2:1 and 3:1 ratio (w/w)
was determined. The presence of PVP improves the solubility of PZQ (0.31
0.01 mg/mL). A maximum of
1.29
0.03 mg/mL of PZQ in solution was achieved for the 3:1 SD (E/E). The amount of PZQ in solution
depends on the amount of polymer and on the preparation method. Solid-state NMR (ssNMR) and DSC
were used to understand this behavior. Results show that PMs are a mixture of crystalline PZQ with the
polymer, while SDs show different degrees of drug amorphization depending on the solvent used. For E/
W SDs, PZQ exists in amorphous and crystalline states, with no clear correlation between the amount of
crystalline PZQ and the amount of PVP. For E/E SDs, formulations with a higher percentage of PZQ are
amorphous with the components miscible in domains larger than 3 nm (1H ssNMR relaxation
measurements). Albeit its higher saturation solubility, the 3:1 E/E PVP:PZQ sample has a significant
crystalline content, probably due to the water introduced by the polymer. High PVP content and small
crystal size account for this result