C H A P T E R 5 9
Antiemetic agents
937
■■
Antiemetics are used to manage nausea and vomiting
in situations in which these actions are not beneficial
and could cause harm to the person.
■■
Antiemetics act by depressing the hyperactive
vomiting reflex, either locally or through alteration of
CNS actions.
■■
The choice of an antiemetic depends on the cause of
the nausea and vomiting, and the expected actions of
the drug.
■■
Antiemetics include the phenothiazines and
centrally acting non-phenothiazine metoclopramide;
anticholinergic/antihistamines; the 5-HT
3
receptor
blockers; and the newest class of antiemetic, the
substance P/neurokinin 1 receptor antagonists.
CHAPTER SUMMARY
■■
Phenothiazines and the non-phenothiazine
metoclopramide are used as antiemetics to depress
the CNS, including the CTZ. People must be
monitored for CNS depression. Photosensitivity and
pink to red-brown colour of the urine are common
adverse effects of these drugs.
■■
Anticholinergic/antihistamine drugs are used to
block the transmission of impulses within the
CNS. They may be particularly effective in treating
motion sickness. People receiving these drugs must
be monitored for parasympathetic blocking effects,
drowsiness and sedation.
■■
The 5-HT
3
blockers are newer antiemetics that
directly block specific receptors in the CTZ to
prevent nausea and vomiting. They are used in cases
of nausea and vomiting associated with antineoplastic
chemotherapy and radiation therapy as well as
postoperative nausea and vomiting.
■■
Most antiemetics cause some CNS depression, with
resultant dizziness, drowsiness and weakness. Care
must be taken to protect the person and advise them
to avoid dangerous situations.
■■
Photosensitivity is another common adverse effect
with antiemetics. People should be protected from
KEY POINTS
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
■
■
Evaluate the effectiveness of the teaching plan
(person can name the drug and dosage, as well as
describe adverse effects to watch for and specific
measures to avoid them).
exposure to the sun and ultraviolet light. Sunscreens
and protective clothing are essential if exposure
cannot be prevented.
Knowing your strengths and weaknesses helps you to
study more effectively. Take a PrepU Practice Quiz
to find out how you measure up!
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