Gastrointestinal behavior of itraconazole in humans – Part 1: Supersaturation from a solid dispersion and a cyclodextrin-based solution
This study evaluated the fasted state gastrointestinal behavior of the lipophilic drug itraconazole, orally administered to healthy volunteers as either a solid dispersion (Sporanox® capsules) or a cyclodextrin-based solution (Sporanox® solution). Following intake of the drug products, gastric and duodenal fluids were aspirated and analyzed for itraconazole concentration, total content and solubilizing capacity. Release of itraconazole from the solid dispersion generated high and metastable supersaturated levels in the stomach, but the dissolved fraction in the duodenum remained extremely low (median 2.5%). After intake of the itraconazole solution, precipitation was limited in the stomach but pronounced in the small intestine. Still, the dissolved fraction of itraconazole in the duodenum (median 38%) appeared much higher than after intake of the solid dispersion, possibly explaining the improved absorption of itraconazole from the solution. As for the solid dispersion, the absorption-enabling ability of the solution appeared mainly related to increased intraluminal concentrations by means of supersaturation. Cyclodextrin-based solubilization of itraconazole occurred only in the case of limited intraluminal dilution, but did not further enhance itraconazole absorption. The obtained data will help to understand critical aspects of supersaturating drug delivery systems and act as direct reference for the optimization of in vitro simulation tools for gastrointestinal drug behavior.