Gastrointestinal and Antiemetic Drugs I. Overview This chapter describes drugs used to treat three common medical conditions involving the gastrointestinal tract: peptic ulcers and gastroesophageal reflux disease (GERD), chemotherapy-induced emesis, and diarrhea and constipation. Many drugs described in other chapters also find application in the treatment of gastrointestinal disorders. For example, the meperidine derivative diphenoxylate , which decreases peristaltic activity of the gut, is useful in the treatment of severe diarrhea, and the corticosteroid dexamethasone has excellent antiemetic properties. Other drugs, (for example, H 2 - receptor antagonists and proton-pump inhibitors (PPIs), are employed to heal peptic ulcers; the selective inhibitors of the serotonin receptors, such as ondansetron or granisetron , which prevent vomiting, are used almost exclusively to treat gastrointestinal tract disorders.
Summary of drugs used to treat peptic ulcer disease.
II. Drugs Used to Treat Peptic Ulcer Disease Although the pathogenesis of peptic ulcer disease is not fully understood, several major causative factors are recognized: nonsteroidal anti-inflammatory drug (NSAID) use, infection with gram-negative Helicobacter pylori, increased hydrochloric acid secretion, and inadequate mucosal defense against gastric acid. Treatment approaches include 1) eradicating the H. pylori infection, 2) reducing secretion of gastric acid with the use of H2-receptor antagonists or PPIs, and/or 3) providing agents that protect the gastric mucosa from damage, such as misoprostol and sucralfate. (Note: If patients are unable to tolerate the above therapies, neutralizing gastric acid with nonabsorbable antacids is an option).
A. Antimicrobial agents Optimal therapy for patients with peptic ulcer disease (both duodenal and gastric ulcers) who are infected with H. pylori requires antimicrobial treatment. To document infection with H. pylori, endoscopic biopsy of the gastric mucosa or various noninvasive methods are utilized, including serologic tests and urea breath tests. Next figure shows a biopsy sample in which H. pylori is closely associated with the gastric mucosa. Eradication of H. pylori results in rapid healing of active peptic ulcers and low recurrence rates (less than 15 percent compared with 60 to 100 percent per year for patients with initial ulcers healed by traditional antisecretory therapy). Successful eradication of H. pylori (80to 90 percent) is possible with various combinations of antimicrobial drugs.
Currently, either triple therapy consisting of a PPI with either metronidazole or amoxicillin plus clarithromycin , or quadruple therapy of bismuth subsalicylate and metronidazole plus tetracycline plus a PPI, are administered for a 2-week course. This usually results in a 90 percent or greater eradication rate. Bismuth salts do not neutralize stomach acid, but they inhibit pepsin and increase the secretion of mucus, thus helping to form a barrier against the diffusion of acid in the ulcer.
- Fall '18
- Gastric Ulcers