Chapter 52: Antiemetic and antinausea

Question 1

• A variety of stimuli can induce nausea and vomiting

Answer 1

, including foul odors or tastes, unpleasant sights, irritation of the stomach or intestines, and certain drugs (ipecac or antineoplastic drugs).

• Two specific types of nausea and vomiting, chemotherapy-induced and postoperative, produce much more intense symptoms and are treated much more aggressively than general nausea and vomiting

Question 2

• Drugs used to relieve nausea and vomiting are called antiemetic drugs.

Answer 2

Antiemetics help to control vomiting, or emesis, and are also useful in relieving or preventing nausea. Antiemetics are used to prevent motion sickness, reduce secretions before surgery, treat delayed gastric emptying, and prevent postoperative nausea and vomiting.

Question 3

• Anticholinergics

Answer 3

work by blocking acetylcholinesterase (Ach) receptors in the vestibular nuclei and reticular formation, preventing areas in the brain from being activated by nauseous stimuli.

also tend to dry GI secretions and reduce smooth muscle spasms, effects that are often helpful in reducing acute GI symptoms, including nausea and vomiting.

Question 4

• Antihistamines

Answer 4

prevent cholinergic stimulation in both the vestibular and reticular systems. Nausea and vomiting occur when these systems are stimulated

Question 5

• Antidopaminergic drugs, although traditionally used for antipsychotic effects, also prevent

Answer 5

nausea and vomiting by blocking dopamine receptors in the chemoreceptor trigger zone (CTZ). Many also have actions similar to those of anticholinergic drugs. They also calm the central nervous system.

Question 6

• Prokinetic drugs, in particular metoclopramide, act as antiemetics by

Answer 6

blocking dopamine receptors in the CTZ, which desensitizes the CTZ to impulses it receives from the GI tract. The primary action is to stimulate peristalsis in the GI tract. This enhances the emptying of stomach contents into the duodenum, as well as intestinal movements.

Question 7

• The serotonin-blocking drugs (granisetron and ondansetron) work by

Answer 7

blocking serotonin receptors located in the GI tract, CTZ, and vomiting center. They are most commonly used for the prevention of chemotherapy-induced nausea and vomiting.

Question 8

• Tetrahydrocannabinol (THC), in a drug class by itself, is the major psychoactive substance in marijuana

Answer 8

Non-intoxicating doses in the form of the drug dronabinol (Marinol) are occasionally used as an antiemetic because of the drug’s inhibitory effects on the reticular formation, thalamus, and cerebral cortex. Dronabinol therapy is used to prevent chemotherapy-induced nausea and vomiting and is associated with postural hypotension

Question 9

• Two commonly used antiemetic drugs may have serious consequences for the patient if they are given via the wrong route.

Answer 9

o	Hydroxyzine (Vistaril) is an antihistamine-class antiemetic that is only to be given either by oral or intramuscular routes.
o	The oral and intramuscular routes are the preferred routes of administration for promethazine (Phenergan). The intravenous route is not the preferred route. If given intraarterially, severe tissue damage, possibly leading to amputation, may occur. Sedation is the most adverse common effect.

Question 10

• Identify any factors precipitating nausea or vomiting;

Answer 10

; note any weight loss; measure baseline vital signs; assess intake and output; examine the skin and mucous membranes, noting turgor and color; and assess and document capillary refill (normal is less than 5 seconds).

Question 11

• One very important concern to reemphasize with scopolamine, which is commonly administered in patch form to prevent motion sickness,

Answer 11

, is the contraindication to its use in patients with narrow-angle glaucoma.

Question 12

• Antidopaminergic drugs, such as promethazine, should be used only after cautious assessment for signs and symptoms

Answer 12

of dehydration and electrolyte imbalance by evaluating skin turgor and examining the tongue for the presence of longitudinal furrows.

Question 13

Extrapyramidal symptoms (EPS), also known as extrapyramidal side effects (EPSE), per wilkipedia

Answer 13

are drug induced movement disorders that include acute and tardive symptoms. These symptoms include dystonia (continuous spasms and muscle contractions), akathisia (motor restlessness), parkinsonism (characteristic symptoms such as rigidity, bradykinesia, and tremor), and tardive dyskinesia (irregular, jerky movements).

Question 14

Tardive dyskinesia per wilkipedia

Answer 14

is a difficult-to-treat and often incurable form of dyskinesia, a disorder resulting in involuntary, repetitive body movements.

Question 15

• Monitor the patient for adverse effects such as

Answer 15

GI upset, drowsiness, lethargy, weakness, extrapyramidal reactions, and orthostatic hypotension during antiemetic therapy.