Mimicking regional and fasted/fed state conditions in the intestine with the mucus-PVPA in vitro model: The impact of pH and simulated intestinal fluids on drug permeability

Intestinal drug absorption following oral administration can be influenced by regional conditions (absorbing surface area, bacterial flora, motility, pH, mucus thickness) and food intake, all of which affect drug solubility and permeability. Therefore, it is crucial to assess the impact of these conditions on the drugability of drugs and formulations. In this study, the ability of the liposome-based mucus-PVPA in vitro permeability model to handle relevant intestinal pH conditions was evaluated, together with the investigation on the pH-dependent solubility and permeability profiles of five model drugs. This study additionally evaluated the impact of all commercially available versions of the fasted and fed state simulated intestinal fluids (SIFs) on the integrity of the barriers, and the permeabilities of one hydrophilic and one lipophilic compound were examined under these conditions. The model was found to be well-functioning in all tested pH conditions, and a pH-dependent trend was found for both solubility and permeability profiles for acidic and basic compounds, according to their degree of ionization. Moreover, the mucus layer and its pH-dependent viscosity particularly influenced the permeation of more lipophilic compounds. The PVPA barriers primarily maintained their functionality in the presence of the fed state SIFs, and the permeability of the two tested compounds showed to be influenced by their hydrophilicity/lipophilicity, their degree of interaction with mucus and by the bile salts and phospholipids content in the SIFs. Overall, the obtained results highlight the relevance of studying the effect that pH, mucus and SIFs have on intestinal drug absorption, and suggest the suitability of the mucus-PVPA model for such investigations.