Cyclodextrin-water soluble polymer ternary complexes enhance the solubility and dissolution behaviour of poorly soluble drugs. Case example: itraconazole.

The aim of the present series of experiments was to improve the solubility and dissolution/precipitation behaviour of a poorly soluble, weakly basic drug, using itraconazole as a case example. Binary inclusion complexes of itraconazole with two commonly used cyclodextrin derivatives and a recently introduced cyclodextrin derivative were prepared. Their solubility and dissolution behaviour was compared with that of the pure drug and the marketed formulation Sporanox®. Ternary complexes were prepared by addition of Soluplus®, a new highly water soluble polymer, during the formation of the itraconazole/cyclodextrin complex. A solid dispersion made of itraconazole and Soluplus® was also studied as a control. Solid state analysis was performed for all formulations and for pure itraconazole using powder X-ray diffraction (pX-RD) and differential scanning calorimetry (DSC). Solubility tests indicated that with all formulation approaches, the aqueous solubility of itraconazole formed with hydroxypropyl-β-cyclodextrin (HP-β-CD) or hydroxybutenyl-β-cyclodextrin (HBen-β-CD) and Soluplus® proved to be the most favourable formulation approaches. Whereas the marketed formulation and the pure drug showed very poor dissolution, both of these ternary inclusion complexes resulted in fast and extensive release of itraconazole in all test media. Using the results of the dissolution experiments, a newly developed physiologically based pharmacokinetic (PBPK) in silico model was applied to compare the in vivo behaviour of Sporanox® with the predicted performance of the most promising ternary complexes from the in vitro studies. The PBPK modelling predicted that the bioavailability of itraconazole is likely to be increased after oral administration of ternary complex formulations, especially when itraconazole is formulated as a ternary complex comprising HP-β-CD or HBen-β-CD and Soluplus®.