Anti-Emetics

Question 1

Vestibular Nucleus Receptors

Answer 1

H1

Ach

Question 2

Vomiting Centre Receptors

Answer 2

Muscarinic

NK1

Question 3

Chemoreceptor Trigger Zone

Answer 3

5HT3
D2
NK1
ENK

Question 4

Stomach

Answer 4

5HT3

DA

Question 5

Serotonin Antagonists

Answer 5

Ondansetron
Prevent activation of VC
Doesn’t affect dopamine receptors, no extra-pyramidal effects
PK: Absorbed well, metabolised by liver
SE: tolerated well

Question 6

Dopamine Antagonists

Answer 6

Domperidone
Competitive D2 antagonist
Inhibit VC and afferent impulses in gut at solitary tract nucleus
SE: Sedation, anticholinergic effects, hypertension, parkinsonism

Question 7

H1 Antagonist

Answer 7

Promethazine
Inhibits neural pathway from VN
May not be primary MOA
Could be sedative effects
SE: Drowsiness, Hypotension, Confusion, Urinary retention

Question 8

Antimuscarinics

Answer 8

Scopolamine
Inhibits muscarinic receptors in Cerebellum
Rapidly and fully distributed in CNS
Particularly effective in motion sickness
SE: Anticholinergic effects when given orally which are reduced transdermally

Question 9

Neurokinin Receptor Antagonists

Answer 9

Aprepitant
Usually given with dexamethasone and 5HT3 antagonist
Prevents acute amd delayed emetic response to chemo e.g. Cisplatin
Blocks action of Substance P on NK1 receptors in CTZ
PK: Metabolised by CYP3A4 and induces it
SE: Constipation, fatigue

Question 10

Cannabinoids

Answer 10

Dronabinol- oral formulation of THC
Cancer chemo- induces emesis refractory
Acts on receptors in CTZ

Question 11

Benzodiazepines

Answer 11

Sedative-hypnotic

Used to control anticipatory nausea and vomiting