1. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. CHAPTER 53 Antiemetic and Antinausea Drugs

2. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Definitions  Nausea  Unpleasant feeling that often precedes vomiting  Emesis (vomiting)  Forcible emptying of gastric, and occasionally, intestinal contents  Antiemetic drugs  Used to relieve nausea and vomiting

3. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. VC and CTZ  Vomiting center (VC)  Chemoreceptor trigger zone (CTZ)  Both located in the brain  Once stimulated, cause the vomiting reflex

4. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc.

5. Mechanism of Action  Many different mechanisms of action  Most work by blocking one of the vomiting pathways, thus blocking the stimulus that induces vomiting

6. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc.

7. Indications  Specific indications vary per class of antiemetics  General use for each type: prevention and reduction of nausea and vomiting

8. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action and Other Indications Anticholinergic drugs (ACh blockers)  Bind to and block acetylcholine (ACh) receptors in the inner ear labyrinth  Block transmission of nauseating stimuli to CTZ  Also block transmission of nauseating stimuli from the reticular formation to the VC  scopolamine Also used for motion sickness Also used for motion sickness

9. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action and Other Indications (cont’d) Antihistamine drugs (H 1 receptor blockers)  Inhibit ACh by binding to H 1 receptors  Prevent cholinergic stimulation in vestibular and reticular areas, thus preventing nausea and vomiting  dimenhydrinate, diphenhydramine, meclizine, promethazine  Also used for motion sickness, nonproductive cough, allergy symptoms, sedation

10. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action and Other Indications (cont’d) Neuroleptic drugs  Block dopamine receptors on the CTZ  chlorpromazine, promethazine, perphenazine, several others  Also used for psychotic disorders, intractable hiccups

11. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action and Other Indications (cont’d) Prokinetic drugs  Block dopamine in the CTZ  Cause CTZ to be desensitized to impulses it receives from the GI tract  Also stimulate peristalsis in GI tract, enhancing emptying of stomach contents  metoclopramide (Reglan), cisapride  Also used for GERD, delayed gastric emptying

12. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action and Other Indications (cont’d) Serotonin blockers  Block serotonin receptors in the GI tract, CTZ, and VC  dolasetron, granisetron, ondansetron  Used for nausea and vomiting in patients receiving chemotherapy and for postoperative nausea and vomiting

13. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action and Other Indications (cont’d) Tetrahydrocannabinoids  Major psychoactive substance in marijuana  Inhibitory effects on reticular formation, thalamus, cerebral cortex  Alter mood and body’s perception of its surroundings

14. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action and Other Indications (cont’d) Tetrahydrocannabinoids (cont'd)  dronabinol (Marinol)  Used for nausea and vomiting associated with chemotherapy, and anorexia associated with weight loss in AIDS patients

15. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Adverse Effects  Vary according to drug used  Stem from their nonselective blockade of various receptors

16. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications  Assess complete nausea and vomiting history, including precipitating factors  Assess current medications  Assess for contraindications and potential drug interactions

17. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  Many of these drugs cause severe drowsiness; warn patients about driving or performing any hazardous tasks  Taking antiemetics with alcohol may cause severe CNS depression  Teach patients to change position slowly to avoid hypotensive effects

18. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d)  For chemotherapy, antiemetics are often given 1 to 3 hours before a chemotherapy drug  Monitor for therapeutic effects  Monitor for adverse effects