Influence of blood flow on intestinal absorption of xenobiotics.

The dependence of intestinal absorption of xenobiotics on the blood flow rate increases from blood flow independent to blood flow limited absorption as the absorbability of the substances increases. Since the absorbed substances are mainly drained by the blood flowing through the subepithelial vessels, not only the total flow rate of an intestinal segment but also the intramural blood flow pattern influences the absorption rate. The villous countercurrent exchange represents an additional resistance to the absorption. In rat jejunum a time-dependent decreases of absorption complicates the analysis of experimental data.