Dissolution properties of praziquantel-beta-cyclodextrin systems.

The purpose of this study was to characterize the dissolution behavior of a poorly water-soluble antischistosomal agent, praziquantel (PZQ), from PZQ-beta-cyclodextrin systems containing 20-100% w/w of drug. Dissolution parameters obtained from the release data of simple physical mixtures and inclusion compounds prepared by the solvent method were employed to characterize the effect of drug loading on the release kinetics of PZQ. All the systems investigated showed improved dissolution in comparison with the free drug due to the ability to form a complex in solution. The systems prepared by the solvent method showed different characteristics and mechanism of dissolution than the physical mixtures: At low beta-cyclodextrin (beta-CD) weight fractions (high drug loading) their dissolution profiles were higher than those of the physical mixtures. At high polymer weight fractions (low drug loading and equimolar ratio) the physical mixtures exhibited a 7-fold higher dissolution rate than the pure drug. The inclusion systems, on the other hand, showed an improvement in the dissolution rate, but to a lesser degree than the physical mixtures. The observed changes in the mechanism of release kinetics of the different PZQ-beta-CD systems were interpreted using the principles of percolation theory and the results of thermal analysis of the physical mixtures and the inclusion compounds.