252 Pharmacology - Antiemetic Drugs

Question 1

Definition of nausea.

Answer 1

Sensation often leading to the urge to vomit

Question 2

Definition of emesis (vomiting).

Answer 2

Forcible emptying of gastric and, occasionally, intestinal contents.

Question 3

List the various classifications of antiemetic and antinausea drugs.

Answer 3

• Anticholinergic drugs
• Antihistamines (histamine 1 [H₁] receptor blockers)
• Antidopaminergic drugs
• Neurokinin antagonists
• Prokinetic drugs
• Serotonin blockers
• Tetrahydrocannabinoids

Question 4

What is the mechanism of action for most antiemetic or antinausea drugs?

Answer 4

Most work by blocking one of the vomiting pathways, thus blocking the stimulus that induces vomiting.

Question 5

What is the mechanism of action for anticholinergic antiemetiic/antinausea drugs?

Answer 5

• Bind to and block acetylcholine 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 vomiting centre

Question 6

Define chemoreceptor trigger zone (CTZ)

Answer 6

The area of the brain that is involved in the sensation of nausea and the action of vomiting.

Question 7

What is the vomiting centre (VC)?

Answer 7

The area of the brain that is involved in stimulating the physiological events that lead to nausea and vomiting.

Question 8

What are the indications for anticholinergics?

Answer 8

• Motion sickness
• secretion reduction before surgery
• nausea and vomiting

Question 9

What are the indications for antihistamines?

Answer 9

• Motion sickness
• Nonproductive cough
• Sedation
• Rhinitis
• Allergy symptoms
• Nausea and vomiting

Question 10

What are the indications for antidopaminergics?

Answer 10

• Psychotic disorders
• intractable hiccups
• nausea and vomiting

Question 11

What are the indications for prokinetics?

Answer 11

• Delayed gastric emptying
• Gastroesophageal reflux
• Nausea and vomiting

Question 12

What are the indications for serotonin blockers?

Answer 12

• Nausea and vomiting associated with chemotherapy
• Postoperative nausea and vomiting

Question 13

What are the indications for tetrahydrocannabinol?

Answer 13

• Nausea and vomiting associated with chemotherapy
• Anorexia associated with weight loss in patients with AIDS and cancer

Question 14

What are some causes of N and V?

Answer 14

• Chemotherapy
• Postoperative
• Anesthesia
• General
• Inner ear infection

Question 15

What class is scopolamine?

Answer 15

anticholinergic

Question 16

What is the mechanism of action of anticholinergic antiemetics?

Answer 16

• Bind to and block acetylcholine 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 vomiting centre

Question 17

What is the mechanism of action of antihistamine antiemetic drugs?

Answer 17

• Inhibit acetylcholine by binding to H₁ receptors
• Prevent cholinergic stimulation in vestibular and reticular areas, thus preventing nausea and vomiting

Question 18

What class of drug are •dimenhydrinate (Gravol^®) and diphenhydramine (Benadryl^®)?

Answer 18

antihistamines

Question 19

What is the mechanism of action of antidopaminergic antiemetic drugs?

Answer 19

Block dopamine receptors in the CTZ

Question 20

What class of drug is •prochlorperazine (Proclorazine^®)?

Answer 20

antidopaminergic

Question 21

What is the mechanism of action of neurokinin receptor antagonists?

Answer 21

• Inhibit substance P/neurokinin 1 receptors in the brain stem
• Used in conjunction with serotonin blockers and glucocorticoids
• Use augments the serotonin blockers and glucocorticoids to inhibit acute and delayed phases of chemotherapy-induced emesis

Question 22

What class does aprepitant belong to?

Answer 22

neurokinin receptor antagonist

Question 23

What is the mechanism of action of prokinetic drugs?

Answer 23

• Block dopamine receptors in the CTZ
• Cause CTZ to be desensitized to impulses it receives from the gastrointestinal tract
• Also stimulate peristalsis in gastrointestinal tract, enhancing emptying of stomach contents

Question 24

What class does metoclopramide belong to?

Answer 24

prokinetic drugs

Question 25

What is the most significant thing to be watching for with metoclopramide?

Answer 25

Long-term use may cause irreversible tardive dyskinesia

Question 26

What is the mechanism of action for serotonin blockers?

Answer 26

* Block serotonin receptors in the gastrointestinal tract, CTZ, and vomiting centre

Question 27

What class of drug does ondansetron belong to?

Answer 27

serotonin blockers

Question 28

What is the mechanism of action of tetrahydrocannabinoids?

Answer 28

* Major psychoactive substance in marihuana * Inhibitory effects on reticular formation, thalamus, cerebral cortex * Alter mood and body’s perception of its surroundings, which may help relieve nausea and vomiting

Question 29

What is doxylamine succinate used for?

Answer 29

used for morning sickness with pregnancy

Question 30

What is pyridoxine hydrochloride used for?

Answer 30

combination known as Diclectin – used for morning sickness – N & V - during pregnancy

Question 31

What is ginger used for in relation to nausea and vomiting?

Answer 31

* Used for nausea and vomiting, including that caused by chemotherapy, morning sickness, and motion sickness * Adverse effects * Anorexia, nausea and vomiting, skin reactions

Question 32

What drug interactions exist for ginger?

Answer 32

* May increase absorption of oral medications * Increase bleeding risk with anticoagulants

Question 33

What contraindications are there for scopolamine?

Answer 33

* glaucoma (due to the pupil dilation effect; may alter intraoccular pressure)

Question 34

What forms is scopolamine available in?

Answer 34

* injectable * patch (applied every 72 hours, onset is 4 hours)

Question 35

True or false: antihistamines can have a paradoxical effect on pediatric patients?

Answer 35

True. It can make them hyperactive

Question 36

What are the contraindications for prochlorperazine?

Answer 36

* Hypersensitivity to phenothiazines * Those in a coma * Those with seizures, encephalopathy, or bone marrow depression

Question 37

What forms does prochlorperazine come in?

Answer 37

Oral and injection

Question 38

What are contraindications for metoclopramide?

Answer 38

* seizure disorders * pheochromocytoma * breast cancer * GI obstruction

Question 39

What is a warning when using ondansetron?

Answer 39

Risk of dysrhythmias, particularly when faster infusion rates are used.

Question 40

What effect does aprepitant have on warfarin?

Answer 40

Induces the metabolism of warfarin sodium and the INR needs to be checked before each cycle.

Question 41

What are contraindications of doxylamine succinate and pyridoxine hydrochloride?

Answer 41

* those with risk of asthmatic attack * patients with narrow angle glaucoma * stenosing peptic ulcer * pyloroduodenal obstruction * bladder-neck obstruction * those taking monoamine oxidase inhibitors

Question 42

What assessments should be done relative to antidopaminergic antiemetic drugs?

Answer 42

* Skin turgor and tongue for longitudinal furrows * Blood pressure and pulse rate (related to effects of orthostatic hypotension and tachycardia)