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Chapter 80

Chapter 80. Other Gastrointestinal Drugs. GI Drugs . Antiemetics Antidiarrheals Drugs for irritable bowel syndrome Drugs for inflammatory bowel disease. Antiemetics. Given to suppress nausea and vomiting Emetic response

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Chapter 80

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  1. Chapter 80 Other Gastrointestinal Drugs

  2. GI Drugs • Antiemetics • Antidiarrheals • Drugs for irritable bowel syndrome • Drugs for inflammatory bowel disease

  3. Antiemetics • Given to suppress nausea and vomiting • Emetic response • Complex reflex after activating vomiting center in medulla oblongata • Several types of receptors involved in emetic response • Serotonin, glucocorticoids, substance P, neurokinin1, dopamine, acetylcholine, and histamine • Many antiemetics interact with one or more of the receptors

  4. Antiemetics • Serotonin receptor antagonists • Granisetron, dolasetron, palonosetron • Ondansetron (Zofran) • First approved for chemotherapy-induced nausea and vomiting (CINV) • Blocks type 3 serotonin receptors on afferent vagal nerve • More effective when used with dexamethasone

  5. Antiemetics • Glucocorticoids • Unknown mechanism of action (MOA) as antiemetic • Methylprednisolone (Solu-Medrol) • Dexamethasone (Decadron) • Commonly used to suppress CINV, but this is not an FDA-approved application • Effective alone and in combination with antiemetics

  6. Antiemetics • Substance P/neurokinin1 antagonists • Aprepitant (Emend) • Blocks neurokinin1-type receptors (for substance P) in the chemoreceptor trigger zone (CTZ) • Prevents postoperative nausea/vomiting and CINV • Prolonged duration of action (delayed CINV and acute) • Adverse effects • Drug interaction

  7. Antiemetics • Benzodiazepines • Lorazepam (Ativan) • Used in combination regimens to suppress CINV • Three primary benefits • Sedation • Suppression of anticipatory emesis • Production of anterograde amnesia

  8. Antiemetics • Dopamine antagonists • Phenothiazines • Block dopamine2 receptors in CTZ • Surgery, cancer, chemotherapy, and toxins • Side effects • Extrapyramidal reactions • Anticholinergic effects • Hypotension and sedation

  9. Antiemetics • Butyrophenones • Haloperidol (Haldol) and droperidol (Inapsine) • Block dopamine2 receptors in CTZ • Postoperative nausea/vomiting, chemotherapy emesis, radiation therapy, and toxins • Side effects • Similar to phenothiazines • May cause prolonged QT and fatal dysrhythmias • Electrocardiographic monitoring needed

  10. Antiemetics • Metoclopramide (Reglan) • Blocks dopamine receptors in CTZ • Postoperative nausea/vomiting, anticancer drug, opioids, toxins, radiation therapy • Cannabinoids • Dronabinol (Marinol) and nabilone (Cesamet) • Related to marijuana • CINV • MOA with emesis unclear • Potential for abuse and psychotomimetic effects

  11. Management of Chemotherapy- Induced Nausea and Vomiting • Three types of emesis • Anticipatory • Occurs before drugs are given • Acute • Onset within minutes to a few hours • Delayed • Onset 1 day or longer after drug received

  12. Management of Chemotherapy-Induced Nausea and Vomiting • Antiemetics are more effective in preventing CINV than suppressing CINV in progress • Give before chemotherapy drugs • Monotherapy and combination therapy may be needed

  13. Drugs for Motion Sickness • Scopolamine • Muscarinic antagonist • Side effects • Dry mouth • Blurred vision • Drowsiness

  14. Drugs for Motion Sickness • Antihistamines • Dimenhydrinate (Dramamine), meclizine (Antivert), cyclizine (Marezine) • Considered anticholinergics—block receptors for acetylcholine and histamine • Side effects • Sedation (H1-receptor blocking) • Dry mouth, blurred vision, urinary retention, constipation (muscarinic receptor blocking)

  15. Diarrhea • Characterized by stools of excessive volume and fluidity and increased frequency of defecation • Symptom of GI disease • Causes • Infection, maldigestion, inflammation, functional disorders of the bowel • Complications • Dehydration and electrolyte depletion

  16. Diarrhea • Management • Diagnosis and treatment of underlying disease • Replacement of lost water and salts • Relief of cramping • Reducing passage of unformed stools • Two major groups of antidiarrheals • Specific antidiarrheal drugs • Nonspecific antidiarrheal drugs

  17. Nonspecific Antidiarrheal Agents • Opioids • Most effective antidiarrheal agents • Activate opioid receptors in GI tract • Decrease intestinal motility • Slow intestinal transit • Allow more fluid to be absorbed • Decrease secretion of fluid into small intestine and increase absorption of fluid and salt • Diphenoxylate (Lomotil) and loperamide (Imodium)

  18. Nonspecific Antidiarrheal Agents • Opioids • Diphenoxylate (Lomotil) • Formulated with atropine to discourage abuse • Opioid used only for diarrhea • High doses can elicit typical morphine-like subjective responses • Loperamide

  19. Nonspecific Antidiarrheal Agents • Difenoxin • Paregoric • Opium tincture • Bismuth subsalicylate • Bulk-forming agents • Anticholinergic antispasmodics

  20. Management of Infectious Diarrhea • General considerations • Variety of bacteria and protozoa can be responsible • Infections are usually self-limited • Many cases require no treatment • Antibiotics should be used only when clearly indicated • Traveler’s diarrhea

  21. Irritable Bowel Syndrome • IBS: most common disorder of GI tract • 20% of Americans affected • 3× higher incidence in women than in men • Characterized by cramping abdominal pain (may be severe) that cannot be explained by structural or chemical abnormalities • May occur with diarrhea, constipation, or both • Considered IBS when symptoms have been present for 12 weeks over the past year

  22. Irritable Bowel Syndrome • Four groups of drugs historically used • American College of Gastroenterology concluded that most of these agents do not have proof of clinical benefits • Antispasmodics • Bulk-forming agents • Antidiarrheals • Tricyclic antidepressants • Two studies suggest that antibiotics or an acid suppressant may be effective for some patients

  23. IBS-Specific Drugs • Alosetron (Lotronex) • Potentially dangerous drug;approved for women only • GI toxicities can cause complicated constipation, leading to perforation and ischemic colitis • Introduced in 2000, withdrawn in less than 10 months, and reintroduced in 2002

  24. IBS-Specific Drugs • Lubriprostone (Amitiza) • Approved for constipation-predominant IBS in women age 18 years and older • Tegaserod (Zelnorm) • Short-term therapy of constipation-predominant IBS

  25. Inflammatory Bowel Disease • IBD: caused by exaggerated immune response against normal bowel flora • Crohn’s disease • Characterized by transmural inflammation • Usually affects terminal ileum (can impact all parts of GI tract) • Ulcerative colitis • Inflammation of the mucosa and submucosa of the colon and rectum • May cause rectal bleeding • May require hospitalization

  26. Drugs for IBD • Not curative: may control disease process • Aminosalicylates (sulfasalazine) • Glucocorticoids (hydrocortisone) • Immunosuppressants (azathioprine) • Immunomodulators (infliximab) • Antibiotics (metronidazole)

  27. Prokinetic Agents • Increase tone and motility of GI tract • GERD, CINV, diabetic gastroparesis • Metoclopramide (Reglan, Maxolon, Octamide) • Blocks receptors for dopamine and serotonin in the CTZ • Increases upper GI motility and suppresses emesis • Cisapride (Propulsid)

  28. Palifermin (Kepivance) • First drug approved for decreasing oral mucositis (OM) • Currently indicated only for patients with hematologic malignancies (can stimulate proliferation of malignant cells of nonhematologic origin) • Synthetic form of human keratinocyte growth factor (KGF) • Stimulates proliferation, differentiation, and migration of epithelial cells

  29. Pancreatic Enzymes • Deficiency of enzymes compromises digestion • Pancreatin: hog or beef pancreas • Pancrelipase: hog pancreas • Preferred because enzyme activity is far greater than that of pancreatin • Enteric-coated microspheres

  30. Drugs Used to Dissolve Gallstones • Chenodiol (chenodeoxycholic acid) • Useful for radiolucent stones (not calcium) • Increases production of bile acids • Most successful in women with low cholesterol levels • Ursodiol (ursodeoxycholic acid) • Does not increase bile acids • Reduces the cholesterol content of bile • Gradual dissolution of stones

  31. Anorectal Preparations • Symptomatic relief of hemorrhoids and other anorectal disorders • Local anesthetics • Hydrocortisone • Emollients • Astringents • Multiple formulations available

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