antiemetics

Question 1

main categories of anti-emetic drugs?

Answer 1

histamine receptor antagonists, serotonin receptor antagonists, muscarinic receptor antagonists, dopamine receptor antagonists, cannabinoids, neurokinin-1 antagonist, corticosteroids

Question 2

what is meant by ‘emesis’?

Answer 2

the act or instance of vomiting. occurs in motion sickness and vestibular disorders.

Question 3

define ‘emetic’ and ‘anti-emetic’:

Answer 3

emetic - agent which causes vomiting. anti-emetic an agent which prevents vomiting

Question 4

where is the vomiting reflex regulated?

Answer 4

in the CNS (medulla), and controlled by the brainstem

Question 5

describe the central pathway:

Answer 5

brain stem emetic control centre - dorsal vagal complex

Question 6

what are the three inputs to the dorsal vagal complex that cause nausea and vomiting?

Answer 6

1) chemo receptor trigger zone (located in the dorsal vagal complex) and is the main site of action of antiemetic drugs. 2) the vagal pathway; reacts to sensory input, and stimuli from the pharynx and GI tract. 3) the vestibular pathway; disorientating motion.

Question 7

what does the chemoreceptor trigger zone react to?

Answer 7

endogenous substances, toxins and drugs.

Question 8

overall action of anti-emetic drugs?

Answer 8

antagonists block the receptors of endogenous mediators of emesis, preventing sickness

Question 9

which anti-emetics target the chemo-receptor trigger zone / emetic centre?

Answer 9

serotonin antagonists, dopamine antagonists, substance P/neuorkinin antagonists.

Question 10

which anti-emetics target the vagal pathway? (sensory)

Answer 10

serotonin antagonists

Question 11

which anti-emetics target the vestibular pathway? (motion)

Answer 11

histamine antagonists, muscarinic antagonists

Question 12

examples of H1 antagonists / antihistamines and their action

Answer 12

cyclizine - motion sickness. cinnarizine - motion sickness, vestibular disorders. promethazine - morning sickness.

Question 13

side effects of antihistamines?

Answer 13

drowsiness, sedation

Question 14

examples of muscarinic antagonists and their action:

Answer 14

hyoscine, scopolamine; used for motion sickness.

Question 15

side effects of muscarinic antagonists?

Answer 15

dry mouth, blurred vision

Question 16

examples of dopamine receptor antagonists?

Answer 16

phenothiazines, prochlorperazine, perphenazine, metoclopramide, domperidone

Question 17

action of phenothiazines?

Answer 17

dopamine receptor antagonists that are used for morning sickness

Question 18

what are dopamine antagonists generally used against?

Answer 18

uraemia, opioid induced emesis, CINV, GI disorders, viral gasteroenteritis

Question 19

side effects of phenothiazines (dopamine antagonists)?

Answer 19

sedative, hypotension, dystonia, dyskinesia

Question 20

examples of serotonin antagonists and their actions?

Answer 20

ondansetron; drug of choice for CINV and PONV. other examples are; granisetron, palnosetron, tropisetron

Question 21

side effects of ondansetron? (serotonin antagonist)

Answer 21

gastro-intestinal disturbances, headache

Question 22

what are neurokinin-1 antagonists and their actions?

Answer 22

active in late phase emesis with cytototxic drugs. main example is aprepitant; used against CINV and PONV.

Question 23

common side effects of aprepitant?

Answer 23

fatigue, listlessness, constipation, diarrhoea, loss of appetite, hiccups

Question 24

examples of cannabinoids?

Answer 24

nabilone, marinol

Question 25

what is nabilone used for?

Answer 25

treatment of CINV, pain management.

Question 26

examples of corticosteroids used as anti-emetics?

Answer 26

dexamethasone

Question 27

action of dexamethasone?

Answer 27

used for vomiting caused by cytotoxic (chemotherapy) - used in combination with dopamine and serotonin antagonists for improved actions.