Differences in Food Effects for 2 Weak Bases With Similar BCS Drug-Related Properties: What Is Happening in the Intestinal Lumen?

Ketoconazole and posaconazole are both Biopharmaceutics Classification System class 2 drugs (highly permeable, poorly soluble), are structurally similar, and are administered at the same doses. Nevertheless, the duodenal concentration profile and the magnitude of the positive food effect observed for these 2 drugs are markedly different. The aim of this study was to investigate, by means of in silico models, the likely mechanism(s) behind such differences. On the basis of the simulations presented here, it seems highly likely that the balance between the degree of supersaturation in the intestinal lumen and the drug flux across enterocyte membrane can explain the massive difference in the relevance of in vivo precipitation for these 2 drugs, when administered in the fasted state. In the fed state, it appears that the slower gastric emptying together with the higher solubility combines to effect better absorption in the case of posaconazole.