Preparation, dissolution and characterization of praziquantel solid dispersions

Solid dispersions of praziquantel (PZQ) containing varying concentrations o f polyvinylpyrrolidone (PVP) with different molecular weights (3000, 11000 and 34000) were prepared in an attempt to improve the solubility and dissol ution rate of PZQ. The physical characteristics of PZQ, physical mixtures a nd solid dispersions were investigated by a variety of analytical methods i ncluding scanning electron microscopy (SEM), differential scanning calorime try (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 r atio of the drug to PVP was smaller (1 : 9). SEM was especially useful in t he verification of possible PZQ inclusion in the PVP matrix due to the morp hological and physical differences between PZQ and PVP, The physical mixtur e 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 w as 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.