Preparation, dissolution and characterization of praziquantel solid dispersions

Solid dispersions of praziquantel (PZQ) containing varying concentrations of polyvinylpyrrolidone (PVP) with different molecular weights (3000, 11000 and 34000) were prepared in an attempt to improve the solubility and dissolution rate of PZQ. The physical characteristics of PZQ, physical mixtures and solid dispersions were investigated by a variety of analytical methods including scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD), The solubility of PZQ in the coprecipitate was greater when PVP of a smaller molecular weight was used. The dissolution rate of the drug in the coprecipitate was faster when the ratio of the drug to PVP was smaller (1 : 9). SEM was especially useful in the verification of possible PZQ inclusion in the PVP matrix due to the morphological and physical differences between PZQ and PVP, The physical mixture and solid dispersion DSC scans did not present a clear endothermic peak, perhaps due to a low PZQ enthalpy. The dissolution rate was significantly increased when the PZQ : PVP ratio was at Least 1 : 5, which agrees with the inclusion of PZQ in the PVP matrix, as observed by SEM, and the amorphous pattern shown by XRD.