Pharmacology of Intestinal Permeation II

Pharmacology of Intestinal Permeation II

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The intestine, particularly the small bowel, represents a large surface (in the adult 2 human approximately 200 m ) through which the body is exposed to its environ ment. A vigorous substrate exchange takes place across this large surface: nutrients and xenobiotics are absorbed from the lumen into the bloodstream or the lymph, and simultaneously, the same types of substrate pass back into the lumen. The luminal surface of the intestine is lined with a qleakyq epithelium, thus the passage of the substrates, in either direction, proceeds via both transcellular and intercellular routes. Simple and carrier-mediated diffusion, active transport, pinocytosis, phagocytosis and persorption are all involved in this passage across the intestinal wall. The term qintestinal permeationq refers to the process of passage of various substances across the gut wall, either from the lumen into the blood or lymph, or in the opposite direction. qPermeabilityq is the condition of the gut which governs the rate of this complex two-way passage. The pharmacologist's interest in the problem of intestinal permeation is twofold: on the one hand, this process determines the bioavailability of drugs and contributes significantly to the pharmacokinetics and toxicokinetics of xeno biotics; on the other hand, the pharmacodynamic effects of many drugs are manifested in a signigicant alteration of the physiological process of intestinal permeation.The overall observed rate of active transport obviously must equal the sum of the rates of transport at all nth sites so that ... This diagram illustrates the manner in which active transport kinetics are altered by changes in f. a low resistance of the anbsp;...


Title:Pharmacology of Intestinal Permeation II
Author:
Publisher:Springer Science & Business Media - 2012-12-06
ISBN-13:

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