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The gastrointestinal tract serves many important functions: digestive, excretory, endocrine, exocrine, and so on. These functions are the targets of several important classes of drugs. Some of these drugs have been discussed previously. This chapter mentions them and discusses in more detail others that do not fall into the classes of agents described previously.

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A. Drugs Used in Acid-Peptic Diseases
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Ulceration and erosion of the lining of the upper portion of the gastrointestinal tract are common problems that manifest as gastroesophageal reflux disease (GERD), gastric and duodenal peptic ulcers, and stress-related mucosal injury. Drugs used in acid-peptic disease reduce intragastric acidity by manipulating systems controlling acid secretion (Figure 59–1), promote mucosal defense or, in the case of peptic ulcers, eradicate the bacterium Helicobacter pylori, which is detectable in over 80% of patients with duodenal ulcers.
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