The Dynamic Intestinal Absorption Model (Diamod®), an in vitro tool to study the interconnected kinetics of gastrointestinal solubility, supersaturation, precipitation, and intestinal permeation processes of oral drugs

This study aimed at developing the Diamod® as a dynamic gastrointestinal transfer model with physically interconnected permeation. The Diamod® was validated by studying the impact of the intraluminal dilution of a cyclodextrin-based itraconazole solution and the negative food effect for indinavir sulfate for which clinical data are available demonstrating that the systemic exposure was strongly mediated by interconnected solubility, precipitation, and permeation processes. The Diamod® accurately simulated the impact of water intake on the gastrointestinal behavior of a Sporanox® solution. Water intake significantly decreased the duodenal solute concentrations of itraconazole as compared to no intake of water. Despite this duodenal behavior the amount of permeated itraconazole was not affected by water intake as observed in vivo. Next to this, the Diamod® accurately simulated the negative food effect for indinavir sulfate. Different fasted and fed state experiments demonstrated that this negative food effect was mediated by an increased stomach pH, entrapment of indinavir in colloidal structures and the slower gastric emptying of indinavir under fed state conditions. Therefore, it can be concluded that the Diamod® is a useful in vitro model to mechanistically study the gastrointestinal performance of drugs.