Dissolution properties of praziquantel–PVP systems

The dissolution behavior of poorly water-soluble anti-schistosomal drug, praziquantel (PZQ) from coprecipitates (dispersions) and physical mixtures of the drug with polyvinylpyrrolidone (PVP) was characterized. The dissolution data obtained for different PZQ–PVP systems covering a range of drug loading from 10% to 100% w/w of PZQ in 10% increments were used in order to compare the release kinetics between the mixtures and the coprecipitates. The parameters estimated from release models showed that the coprecipitates exhibited an increase in the release rate in relation to intact PZQ but to a lesser extent than the equivalent physical mixtures. Furthermore, they exhibited different release behavior than the physical mixtures. According to solubility studies of PZQ in the presence of PVP the formation of a PZQ–PVP complex can be assumed. This hypothesis led to consistent interpretations of the dissolution profiles. In the coprecipitates the presence of PVP led to near zero-order release. The release kinetics were interpreted in terms of critical percolation thresholds according to the percolation theory.