MISCELLANEOUS GI DRUGS
Additional drugs in classes of their own are also used in the treatment and/or prevention of various GI condi-tions. They include misoprostol, sucralfate, and oc-treotide.
Prostaglandins of the A, E, and I type inhibit gastric acid secretion. The prostaglandins also stimulate in-creased mucus and bicarbonate secretion by gastric mu-cosa. Misoprostol (Cytotec), which is an analogue of prostaglandin E1, has been approved for use in the pre-vention of nonsteroidal antiinflammatory drug–induced ulceration. It also is approved in other countries for the treatment of peptic ulcer disease. Misoprostol is ab-sorbed rapidly after oral administration and is hy-drolyzed to the active compound. It is metabolized by the liver and excreted mainly in the urine. Adverse ef-fects include crampy abdominal pain, dose-related diar-rhea, and uterine contractions. The last-named effect has led to its use in the control of postpartum bleeding .
Sucralfate (Carafate) is an aluminum hydroxide–sul-fated sucrose complex that is only minimally absorbed from the GI tract. After exposure to gastric acid, the compound becomes negatively charged, creating a vis-cous adherent complex. This complex is believed to in-hibit back-diffusion of H+ . Other effects are a direct re-duction in pepsin activity and a slight rise in tissue prostaglandin levels. Stimulation of a cytoprotection mechanism may therefore assist mucosal healing. The drug has no acid-buffering capacity.
Sucralfate is frequently used for prophylaxis of stress-induced gastritis in patients in intensive care units. It has also been successfully used in small num-bers of patients as a suspension enema to treat radiation proctitis.
Constipation is the main side effect associated with its oral use. As with other aluminum compounds, the drug may bind phosphorus, resulting in secondary hy-pophosphatemia. Binding to a number of other coad-ministered medications may result in a significant re-duction in their bioavailability.
Octreotide (Sandostatin) is a synthetic somatostatin analogue. It is used in a variety of situations and must be given subcutaneously or intravenously. Most commonly, it is used as a continuous intravenous infusion in pa-tients hospitalized with bleeding varices, because it decreases splanchnic circulation and therefore reduces portal pressures.
A long-acting depot form is approved for the suppression of severe diarrhea and flushing as-sociated with malignant carcinoid syndrome and for the treatment of the profuse watery diarrhea associated with vasoactive intestinal peptide tumor.
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