Intestine agents promoting

Agents promoting digestion and absorption 115 Drugs acting on intestinal mucosa 115... 

Castor oil is metabolized in the GI tract to an active compound, ricinoleic acid, which stimulates secretory processes, decreases glucose absorption, and promotes intestinal motility, primarily in the small intestine. Castor oil usually results in a bowel movement within 1 to 3 hours of administration. Because the agent has such a strong purgative action, it should not be used for the routine treatment of constipation. 

Gastrointestinal tract. Serotonin released from myenteric neurons or enterochromaffin cells acts on 5-HT3 and 5-HT4 receptors to enhance bowel motility and enteral fluid secretion Cisapride is a proldnetic agent that promotes propulsive motor activity in the stomach and in small and large intestines. It is used in motility disorders. Its mechanism of action is unclear, but stimulation of 5HT4 receptors may be important... 

Antiflatidents (carminatives) serve to alleviate meteorism (excessive accumulation of gas in the gastrointestinal tract). Aborad propulsion of intestinal contents is impeded when the latter are mixed with gas bubbles. Defoaming agents, such as dimethicone (dimethyl-polysiloxane) and simethicone, in combination with charcoal, are given orally to promote separation of gaseous and semisolid contents. 

Iron can only be resorbed by the bowel in bivalent form (i.e., as Fe " ). For this reason, reducing agents in food such as ascorbate (vitamin C see p. 368) promote iron uptake. Via transporters on the luminal and basal side of the enterocytes, Fe " enters the blood, where it is bound by transferrin. Part of the iron that is taken up is stored in the bowel in the form of ferritin (see below). Heme groups can also be resorbed by the small intestine. 

Narasin is effective against all intestinal and cecal coccidia if administered continuously in the feed. It is used for treatment of Eimeria species in broiler chickens at a dosage of 60-80 ppm in the feed. Narasin has been also used as a growth-promoting agent. However, it should not be given to laying hens or to other species of birds or animals to which it is toxic. 

As recently as 1980 it was estimated that there were 100 million cases of acute diarrhea in Asia, Africa, and Latin America 3 in 1991 there were four million deaths among children under five years of age.b The causative agents are bacteria and one of the most dangerous is Vibrio cholerae, which multiplies in the small intestine and secretes an exotoxin. Cholera toxin causes such a rapid loss of fluid and salts from the body that death occurs very quickly, even in adults. There is little cellular damage and almost all deaths can be prevented by intravenous administration of water, salts, and the antibiotic tetracycline. Fluids can also be given orally if glucose, which promotes intestinal absorption, is included with the Na+, K+, Cl, and HC03 salts.b... 

Tea brewed from boiled leaves has been used to treat sexually transmitted diseases and intestinal cramps, and to stimulate urination. The leaves are soaked in water, producing an extract that is used as a bath for rheumatism and chickenpox. The dried powdered leaves may be used as a dusting powder for sores, and are mixed with badger oil to make an ointment used on bums to aid new skin formation. Today, chaparral is promoted as an anticancer agent. 

Azone (l-Dodecylazacycloheptan-2-one) and related compounds have been studied as transdermal penetration and oral absorption enhancers. Although some efficacy has been shown, an emulsifying agent appears to be necessary for azone to penetrate the intestinal mucosal membrane in order to promote drug absorption. One study reported the absence of gross morphological damage after exposure of mucosa to azone but additional information on the effect of azone on overall mucosa structure is not avalable. 

True antisecretory agents, those that block a biochemical process that promotes intestinal fluid secretion, are not available for clinical use in horses. Loperamide can reduce the volume of diarrhea in foals with a primarily small intestinal secretory disorder. However, treated foals may become colicky as a result of fluid distention in the intestines because the mechanism of action is primarily retention of fluid within the intestine. Also, retention of intestinal content may promote the proliferation of enteropathogens. The enkephalinase inhibitor racecadotril appears to have true antisecretory effect in animal models and in humans with diarrhea (Izzo et al 1998). Its safety or effectiveness in foals and horses has not been reported. 

The gastrointestinal tract is a frequent site for adverse effects of antimicrobial drugs, primarily because of disruption of normal intestinal microbial populations and proliferation of enteropatho-gens. Diarrhea, often with accompanying signs of endotoxemia, is the usual clinical manifestation. Antimicrobial agents known to be, or implicated in being, associated with antimicrobial-induced diarrhea include penicillin, ceftiofur, lincomycin, tetracycline, erythromycin and the potentiated sulfonamides. Erythromycin can also promote diarrhea via its motilide activity. 

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