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Chapter 52
Antiemetic and Antinausea Drugs
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Definitions

Nausea


Emesis (vomiting)


Unpleasant feeling that often precedes vomiting
Forcible emptying of gastric, and occasionally,
intestinal contents
Antiemetic drugs

Used to relieve nausea and vomiting
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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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Antiemetics and Antinausea Drugs






Anticholinergic drugs
Antihistamines (histamine 1 [H1] receptor
blockers)
Antidopaminergic drugs
Prokinetic drugs
Serotonin blockers
Tetrahydrocannabinoids
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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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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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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.
B.
C.
D.
Cataracts
Narrow-angle glaucoma
Presbyopia
Detached retina
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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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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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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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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.
B.
C.
D.
metoclopramide (Reglan)
meclizine (Antivert)
aprepitant (Emend)
phosphorated carbohydrate solution (Emetrol)
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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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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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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.
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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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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.
B.
C.
D.
phosphorated carbohydrate solution (Emetrol)
aprepitant (Emend)
palonosetron (Aloxi)
dolasetron (Anzemet)
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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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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.
B.
C.
D.
Prokinetics
Antidopaminergics
Tetrahydrocannabinoids
Serotonin blockers
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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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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.
B.
C.
D.
furosemide (Lasix)
acetaminophen (Tylenol)
warfarin (Coumadin)
calcium supplements
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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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Nursing Implications (cont’d)
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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
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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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