For Determining drug permeability in human intestine. three methods are there absolute bioavailability,mass balance studies and human intestinal perfusion studies for human intestinal perfusion studies however FDA also recommend possible methods not involving human subjects including in vivo or in situ intestinal perfusion in suitable animal models.&or in vitro permeability methods using existed intestinal tissue or monolayer of epithelial cells usually the CaCO2 cell system.
