Chapter 50: Adult Gastrointestinal Medications

Acid-control medications form a foundational category, including antacids that neutralize gastric acid through chemical reaction and elevate pH to inactivate pepsin, with specific formulations presenting distinct side effect profiles related to their chemical composition. Gastric protectants such as misoprostol and sucralfate work through different mechanisms, with misoprostol suppressing acid secretion while enhancing mucosal blood flow, whereas sucralfate creates a physical barrier. Histamine receptor antagonists and proton pump inhibitors both suppress acid secretion but act at different physiological sites, with important drug interaction considerations particularly relevant to cimetidine's hepatic enzyme inhibition. Treatment of Helicobacter pylori infection requires combination therapy to prevent antimicrobial resistance, typically employing triple or quadruple regimens. Gastrointestinal motility disorders respond to prokinetic agents like metoclopramide, which carries risks of extrapyramidal side effects, while antiemetic medications address nausea through serotonin antagonism, glucocorticoid action, or dopamine blockade. Bowel medications encompass laxatives categorized by mechanism—bulk-forming, stimulant, emollient, and osmotic agents—and antidiarrheals that reduce intestinal motility, each with specific clinical applications and contraindications. Management of inflammatory bowel diseases and irritable bowel syndrome employs distinct pharmacological approaches ranging from aminosalicylates to immunomodulators, with syndrome-specific medications like alosetron requiring specialized risk management protocols. Hepatic and biliary medications address cholesterol management through bile acid sequestration and treat hepatic encephalopathy by facilitating ammonia elimination, while pancreatic enzyme replacements compensate for enzymatic deficiency to improve nutrient absorption and reduce steatorrhea.