title: Concentration profile in the intestinal tract and drug absorption model: two-dimensional laminar flow in a circular porous tube.
abstract: The calculation method of the concentration profile in the intestinal tract was developed by adapting the two-dimensional laminar flow in a circular porous tube to the fluid flow and considering a small water absorption or secretion in the intestinal perfusion experiment. The concentration profile was changed by the axial component of velocity, the radial component of velocity, the membrane permeability coefficient, the reflection coefficient and so on. According to the calculated values, the concentration decreased from the center of the intestinal tract to the intestinal membrane as well as from the inlet to the outlet of the intestinal tract. The concentration at the aqueous-intestinal membrane interface increased when water was absorbed and decreased when water was secreted. Consequently, the drug absorption (or secretion), not only because of the effect of the solvent drag but also because of the increase (or decrease) of the concentration gradient at the aqueous-intestinal membrane interface. Using the proposed model in the present study, the concentration at the aqueous-intestinal membrane interface can be calculated directly under the various conditions. Therefore, the true membrane permeability coefficient can be obtained by a graphic method, without correcting the apparent membrane permeability coefficient by the effective thickness of the aqueous diffusion layer (the unstirred water layer).
mesh_terms: D000818:Animals; D002463:Cell Membrane Permeability; D005769:Gastrointestinal Motility; D007408:Intestinal Absorption; D008954:Models, Biological; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D051381:Rats; D013997:Time Factors
chemical_list: D004364:Pharmaceutical Preparations