Validation of a differential in situ perfusion method with mesenteric blood sampling in rats for intestinal drug...

The present study explored the feasibility of a differential setup for the in situ perfusion technique with mesenteric cannulation in rats to assess drug interactions at the level of intestinal absorption. In contrast to the classic, parallel in situ perfusion setup, the differential approach aims to identify intestinal drug interactions in individual animals by exposing the perfused segment to a sequence of multiple conditions. First, the setup was validated by assessing the interaction between the P-glycoprotein (P-gp) inhibitor verapamil and the transport probes atenolol (paracellular transport), propranolol (transcellular) and talinolol (P-gp mediated efflux). While transport of atenolol and propranolol remained constant for the total perfusion time (2 h), a verapamil-induced increase in talinolol transport was observed within individual rats (between 3.2- and 5.2-fold). In comparison with the parallel setup, the differential in situ perfusion approach enhances the power to detect drug interactions with compounds that exhibit strong subject-dependent permeability. This was demonstrated by identifying an interaction between amprenavir and ketoconazole (P-gp and CYP3A inhibitor) in five out of seven rats (permeability increase between 1.9- and 4.2-fold), despite high inter-individual differences in intrinsic permeability for amprenavir. In combination with an increased throughput (up to 300%) and a reduced animal use (up to 50%), the enhanced power of the differential approach improves the utility of the biorelevant in situ perfusion technique with mesenteric blood sampling to elucidate the intestinal interaction profile of drugs and drug candidates.