Chapter 52

Antiemetic and Antinausea Drugs

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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

Definitions

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Vomiting center (VC) Chemoreceptor trigger zone (CTZ)

Both located in the brain Once stimulated, cause the vomiting reflex

Vomiting Center and Chemoreceptor Trigger Zone

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Anticholinergic drugs Antihistamines (histamine 1 [H1] receptor

blockers) Antidopaminergic drugs Prokinetic drugs Serotonin blockers Tetrahydrocannabinoids

Antiemetics and Antinausea Drugs

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Many different mechanisms of action Most work by blocking one of the vomiting

pathways, thus blocking the stimulus that induces vomiting

Antiemetics and Antinausea Drugs: Mechanism of Action

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Specific indications vary per class of antiemetics General use for each type: prevention and

reduction of nausea and vomiting

Indications

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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)  

Mechanism of Action and Other Indications

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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?

A.Cataracts

B.Narrow-angle glaucoma

C.Presbyopia

D.Detached retina

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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)

Mechanism of Action and Other Indications (cont’d)

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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

Mechanism of Action and Other Indications (cont’d)

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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

Mechanism of Action and Other Indications (cont’d)

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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?

A.metoclopramide (Reglan)

B.meclizine (Antivert)

C.aprepitant (Emend)

D.phosphorated carbohydrate solution (Emetrol)

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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)

Mechanism of Action and Other Indications (cont’d)

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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

Mechanism of Action and Other Indications (cont’d)

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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

A. prevent recurrence of the chemotherapy-induced nausea and vomiting.

B. prevent stress ulcers.

C. improve his mood.

D. stimulate his appetite.17Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Tetrahydrocannabinoids (THC) (cont’d) dronabinol (Marinol) Used for nausea and vomiting associated with

chemotherapy, and anorexia associated with weight loss in AIDS patients

Mechanism of Action and Other Indications (cont’d)

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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?

A.phosphorated carbohydrate solution (Emetrol)

B.aprepitant (Emend)

C.palonosetron (Aloxi)

D.dolasetron (Anzemet)19Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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

Miscellaneous Antinausea Drugs

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Vary according to drug used Stem from their nonselective blockade of various

receptors

Adverse Effects

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Classroom Response Question

Which group of drugs used to treat nausea does the nurse identify as most likely to cause a prolonged QTc interval?

A.Prokinetics

B.Antidopaminergics

C.Tetrahydrocannabinoids

D.Serotonin blockers

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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

Herbal Products: Ginger

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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?

A.furosemide (Lasix)

B.acetaminophen (Tylenol)

C.warfarin (Coumadin)

D.calcium supplements

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Assess complete nausea and vomiting history, including precipitating factors

Assess current medications Assess for contraindications and potential drug

interactions

Nursing Implications

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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

Nursing Implications (cont’d)

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For chemotherapy, antiemetics are often given 30 to 60 minutes before chemotherapy begins

Monitor for therapeutic effects Monitor for adverse effects

Nursing Implications (cont’d)

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