Human and simulated intestinal fluids as solvent systems to explore food effects on intestinal solubility and permeability.

The mixed micelles and vesicles present in the intraluminal environment of the postprandial state exhibit suitable solubilizing capacities for lipophilic drugs. This increase in solubility, however, is accompanied by a decrease in the free fraction caused by micellar entrapment of these lipophilic compounds. In this study, both simulated and aspirated human intestinal fluids of fasted and fed state conditions were used to evaluate the influence of food on the intestinal disposition of a series of structurally related β-blockers, with varying logP values. Using the in situ intestinal perfusion technique with mesenteric blood sampling in rats, it was demonstrated that fed state conditions significantly decreased the absorptive flux of the more lipophilic compounds metoprolol, propranolol and carvedilol, whereas the influence on the flux of the hydrophilic β-blocker atenolol was limited. The solubility of BCS class II compound carvedilol was found to increase significantly in simulated and aspirated media of the fed state. Intestinal perfusions using intestinal media saturated with carvedilol, revealed a higher flux in the fasted state compared to the fed state, despite the higher solubility in the fed state. This study underscores the importance of addressing the complex nature of the behavior of compounds in the intraluminal environment in fasted and fed state conditions. Moreover, our data point out the value of studying the effect of food on both solubility and permeability using biorelevant experimental conditions.