1. Antiemetic and Antinausea Drugs
Chapter 52
Antiemetic and Antinausea Drugs
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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
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3. Vomiting Center and Chemoreceptor Trigger Zone
Vomiting center (VC)
Chemoreceptor trigger zone (CTZ)
Both located in the brain
Once stimulated, cause the vomiting reflex
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5. Antiemetics and Antinausea Drugs
Anticholinergic drugs
Antihistamines (histamine 1 [H1] receptor blockers)
Antidopaminergic drugs
Prokinetic drugs
Serotonin blockers
Tetrahydrocannabinoids
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6. Antiemetics and Antinausea Drugs: Mechanism of Action
Many different mechanisms of action
Most work by blocking one of the vomiting pathways, thus blocking the stimulus that induces vomiting
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Indications
Specific indications vary per class of antiemetics
General use for each type: prevention and reduction of nausea and vomiting
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9. 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 (Transderm-Scōp, Scopace)  
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10. Classroom Response Question
The nurse is preparing to administer scopolamine to a patient. It is most important for the nurse to determine if the patient has a history of which condition?
Cataracts
Narrow-angle glaucoma
Presbyopia
Detached retina
Correct answer: B
Rationale: The nurse should only administer the anticholinergic drug scopolamine after careful assessment of the patient’s health history and medication history. One very important concern to reemphasize with scopolamine, which is commonly administered in patch form to prevent motion sickness, is the contraindication to its use in patients with narrow-angle glaucoma. If the patient has a history of this disorder, then another antiemetic or antinausea drug should be used.
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11. Mechanism of Action and Other Indications (cont’d)
Antihistamine drugs (H1 receptor blockers)
Inhibit ACh by binding to H1 receptors
Prevent cholinergic stimulation in vestibular and reticular areas, thus preventing nausea and vomiting
Also used for motion sickness, nonproductive cough, allergy symptoms, sedation
Examples
dimenhydrinate (Dramamine)
diphenhydramine (Benadryl)
meclizine (Antivert)
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12. Mechanism of Action and Other Indications (cont’d)
Antidopaminergic drugs
Block dopamine receptors in the CTZ
Also used for psychotic disorders, intractable hiccups
Examples
prochlorperazine (Compazine)
promethazine (Phenergan)
droperidol: Use is controversial because of associated cardiac dysrhythmia
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13. Mechanism of Action and Other Indications (cont’d)
Prokinetic drugs
Block dopamine receptors 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
Also used for gastroesophageal reflux disease (GERD), delayed gastric emptying
metoclopramide (Reglan)
Long-term use may cause irreversible tardive dyskinesia
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14. Classroom Response Question
A patient is receiving a continuous tube feeding via a PEG tube. Which drug would most likely be prescribed for this patient?
metoclopramide (Reglan)
meclizine (Antivert)
aprepitant (Emend)
phosphorated carbohydrate solution (Emetrol)
Correct answer: A
Rationale: Metoclopramide is a prokinetic drug that promotes the movement of substances through the gastrointestinal tract and increases gastrointestinal motility. This action is helpful in preventing aspiration in those receiving tube feedings.
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15. Mechanism of Action and Other Indications (cont’d)
Serotonin blockers
Block serotonin receptors in the GI tract, CTZ, and VC
Used for nausea and vomiting in patients receiving chemotherapy and for postoperative nausea and vomiting
Examples
dolasetron (Anzemet)
granisetron (Kytril)
ondansetron (Zofran)
palonosetron (Aloxi)
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16. 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, which may help relieve nausea and vomiting
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17. Classroom Response Question
A patient with terminal cancer has not had chemotherapy for a few weeks and has had no nausea or vomiting since then. However, he is taking dronabinol twice a day. The reason for the dronabinol order is to
prevent recurrence of the chemotherapy-induced nausea and vomiting.
prevent stress ulcers.
improve his mood.
stimulate his appetite.
Correct answer: D
Rationale: Dronabinol is used as an appetite stimulant in patients who are experiencing nutritional wasting due to cancer and cancer treatment.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

18. Mechanism of Action and Other Indications (cont’d)
Tetrahydrocannabinoids (THC) (cont’d)
dronabinol (Marinol)
Used for nausea and vomiting associated with chemotherapy, and anorexia associated with weight loss in AIDS patients
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19. Classroom Response Question
A patient is 2 months pregnant. She comes to the clinic complaining of severe morning sickness. She has tried numerous non-pharmacologic measures to relieve the morning sickness, but they have not worked. The nurse anticipates the use of which antinausea drug?
phosphorated carbohydrate solution (Emetrol)
aprepitant (Emend)
palonosetron (Aloxi)
dolasetron (Anzemet)
Correct answer: A
Rationale: Phosphorated carbohydrate solution (Emetrol) is a mint-flavored, pleasant-tasting oral solution used to relieve nausea. It works by direct local action on the walls of the GI tract, where it reduces cramping caused by excessive smooth muscle contraction. It can be used to control mild cases of nausea and vomiting. It does not have a pregnancy category rating, but one of its listed unlabeled (non–FDA-approved) uses is for treatment of morning sickness during pregnancy. The other drugs are not indicated for use in pregnancy.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

20. Miscellaneous Antinausea Drugs
phosphorated carbohydrate solution (Emetrol)
Mint-flavored oral solution
Used off label for treatment of morning sickness
aprepitant (Emend)
Used for the prevention of nausea and vomiting associated with highly emetogenic cancer chemotherapy regimens
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Adverse Effects
Vary according to drug used
Stem from their nonselective blockade of various receptors
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22. Classroom Response Question
Which group of drugs used to treat nausea does the nurse identify as most likely to cause a prolonged QTc interval?
Prokinetics
Antidopaminergics
Tetrahydrocannabinoids
Serotonin blockers
Correct answer: D
Rationale: The serotonin blockers have the potential to cause prolonged QTc interval.
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23. Herbal Products: Ginger
Used for nausea and vomiting, including that caused by chemotherapy, morning sickness, and motion sickness
Adverse effects
Anorexia, nausea and vomiting, skin reactions
Drug interactions
May increase absorption of oral medications
Increase bleeding risk with anticoagulants
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24. Classroom Response Question
A patient tells the nurse that he takes ginger almost every day for nausea. It is most important for the nurse to determine if the patient is taking which medication?
furosemide (Lasix)
acetaminophen (Tylenol)
warfarin (Coumadin)
calcium supplements
Correct answer: C
Rationale: Use of ginger can increase absorption of all oral medications and may theoretically increase bleeding risk with anticoagulants (e.g., warfarin [Coumadin]) or antiplatelet drugs (e.g., clopidogrel [Plavix]).
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Nursing Implications
Assess complete nausea and vomiting history, including precipitating factors
Assess current medications
Assess for contraindications and potential drug interactions
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26. 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 positions slowly to avoid hypotensive effects
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27. Nursing Implications (cont’d)
For chemotherapy, antiemetics are often given 30 to 60 minutes before chemotherapy begins
Monitor for therapeutic effects
Monitor for adverse effects
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