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pathopharm exam 4
CHAPTER 80
| Question | Answer |
|---|---|
| GI Drugs | Antiemetics Antidiarrheals Drugs for irritable bowel syndrome Drugs for inflammatory bowel disease |
| Antiemetics ARE? Many antiemetics interact with one or more of the receptors | suppress nausea and vomiting Emetic response Complex reflex that occurs after activation of vomiting center in the medulla oblongata receptors SEROTONIN, glucocorticoids, substance P, neurokinin1, dopamine, acetylcholine, histamine |
| Serotonin receptor antagonists ? •Blocks type 3 serotonin receptors on afferent vagal nerve •More effective when used with dexamethasone | Ondansetron [Zofran] 1ST APPROVED chemotherapy-induced nausea and vomiting (CINV) •prevent nausea and vomiting DUE TO radiotherapy and anesthesia ADR= Headache, diarrhea, dizziness, prolonged QT interval, risk of torsades de pointes |
| Glucocorticoids | Unknown mechanism of action (MOA) as antiemetic Dexamethasone Commonly used to suppress CINV; however, this is not an application approved by the U.S. Food and Drug Administration (FDA) Effective alone and in combination with antiemetics |
| Benzodiazepines? | Lorazepam [Ativan] Used in combination regimens to suppress CINV Three primary benefits: •Sedation •Suppression of anticipatory emesis •Production of anterograde amnesia |
| Dopamine antagonists | Phenothiazines: Prochlorperazine Block dopamine2 receptors in CTZ •Surgery, cancer, chemotherapy, and toxins •Side effects Extrapyramidal reactions Anticholinergic effects Hypotension and sedation |
| Cannabinoids | Dronabinol [Marinol] Related to marijuanaCINV MOA with emesis unclear Potential for abuse and psychotomimetic effects |
| 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 administration |
| Management of Chemotherapy-Induced Nausea and Vomiting | Antiemetics are more effective in preventing CINV than in suppressing CINV in progress Give before chemotherapy drugs Monotherapy and combination therapy may be needed |
| Nausea and Vomiting of Pregnancy | First-line therapy consists of a two-drug combination: Doxylamine plus vitamin B6 Hyperemesis gravidarum: Dehydration, ketonuria, hypokalemia, and loss of 5% or more of body weight Nondrug measures |
| LAST-LINE OF DEFENSE | Prochlorperazine, metoclopramide, and ondansetron; methylprednisolone may be tried as a last resort, but only after 10 weeks’ gestation-acupuncture, ginger, snacks |
| Drugs for Motion Sickness | Scopolamine Muscarinic antagonist Patch goes behind the ear Side effects•Dry mouth•Blurred vision•Drowsiness |
| Drugs for Motion Sickness S/E-Sedation (H1 receptor blocking) •Dry mouth, blurred vision, urinary retention, constipation (muscarinic receptor blocking) | Antihistamines Dimenhydrinate, meclizine, cyclizine Considered anticholinergics; block receptors for acetylcholine and histaminE |
| Diarrhea | Characterized by stools of excessive volume and fluidity and increased frequency of defecationSymptom of GI disease Causes-Infection, maldigestion, inflammation, functional disorders of the bowel Complications Dehydration and electrolyte depletion |
| Diarrhea | Management Diagnosis and treatment of underlying disease Replacement of lost water and salts Relief of crampingReducing passage of unformed stools Two major groups of antidiarrheals Specific antidiarrheal drugs Nonspecific antidiarrheal drugs |
| Nonspecific Antidiarrheal Agents Most commonly used: Diphenoxylate [Lomotil] and loperamide [Imodium] •Decrease secretion of fluid into small intestine and increase absorption of fluid and salt | Opioids Most effective antidiarrheal agents Activate opioid receptors in GI tract •Reduce intestinal motility •Slow intestinal transit• Allow more fluid to be absorbed |
| Diphenoxylate [Lomotil] | Formulated with atropine to discourage abuse •Opioid used only for diarrhea •High doses can elicit typical morphine-like subjective responses |
| Loperamide [Imodium] | Structural analog of meperidine •Used to treat diarrhea and to reduce the volume of discharge from ileostomies •Little or no potential for abuse |
| Management of Infectious Diarrhea Many cases require no treatment Variety of bacteria and protozoa can be responsible | Infections are usually self-limited Antibiotics should be used only when clearly indicated: Salmonella, Shigella, Campylobacter, or Clostridium infectionsTraveler’s diarrheaEscherichia coli: Usually self-limitingCiprofloxacin, norfloxacin |
| Irritable Bowel Syndrome (IBS) | Most common disorder of GI tract Affects 20% of Americans Incidence in women is 3 times higher than in men Characterized by cramping abdominal pain (may be severe) that cannot be explained by structural or chemical abnormalities |
| Irritable Bowel Syndrome (IBS) American College of Gastroenterology has concluded there is no proof of clinical benefit for most of these agents: | May occur with diarrhea, constipation, or bothConsidered IBS when symptoms have been present for 12 weeks over the past year Four groups of drugs historically used Antispasmodics •Bulk-forming agents •Antidiarrheals •Tricyclic antidepressants |
| IBS-Specific Drugs | Alosetron [Lotronex] For Diarrhea-predominant IBS Potentially hazardous drug; approved for women only GI toxicities can cause complicated constipation, leading to perforation and ischemic colitis Risk management programDrug interactions |
| IBS-Specific Drugs | Lubiprostone [Amitiza] Approved for constipation-predominant IBS (IBS-C) in women age 18 years or olderModest benefits |
| nflammatory Bowel Disease (IBD) Caused by exaggerated immune response to normal bowel flora | Crohn’s disease Usually affects terminal ileum (can affect all parts of GI tract) Ulcerative colitis Inflammation of the mucosa and submucosa of the colon and rectumMay cause rectal bleeding May require hospitalization |
| Drugs for IBD | Not curative; may control disease process 5-Aminosalicylates (sulfasalazine) Glucocorticoids (budesonide) Immunosuppressants/Immunomodulators(mercaptopurine/infliximab) |
| 5-Aminosalicylates | Sulfasalazine [Azulfidine] 5-ASA reduces inflammation; it also suppresses prostaglandin synthesis and migration of inflammatory cells into affected region Most effective against acute episodes of mild to moderate ulcerative colitisAdverse effects |
| Glucocorticoids | Budesonide mild to moderate Crohn’s disease that involves the ileum and ascending colonProlonged use of glucocorticoids can cause severe : ADR= adrenal suppression, osteoporosis, increased susceptibility to infection, and a cushingoid syndrome |
| Immunosuppressants Reserved for patients who have not responded to traditional therapy | Azathioprine [Imuran] and mercaptopurine [Purinethol] Induce and maintain remission in both ulcerative colitis and Crohn’s disease Onset of effects may be delayed for up to 6 monthsADR= pancreatitis and neutropenia |
| A patient is experiencing chemotherapy-induced nausea. Which prescribed medication would be most effective for this patient? | Ondansetron is a serotonin receptor antagonist and is the most effective drug available for suppressing nausea and vomiting caused by chemotherapy. |
| A patient with irritable bowel syndrome is prescribed alosetron [Lotronex]. Before this drug is administered, it is most important for the nurse to do what? | Ask the patient about any problems with constipation. Patients should not take alosetron if constipation develops. Impaction, bowel obstruction, and perforation can occur. |
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