10. Antiemetics Flashcards
Which agents act on the vestibular nuclei?
Muscarinic receptor antagonists
H1 receptor antagonists
Name a muscarinic receptor antagonist
Hyoscine hydrobromide
How do muscarinic receptor antagonists work?
Competitive blockade of muscarinic acetylcholine receptors
- in vestibular nuclei
- also at CTZ
- but also at many other parts of the body
What are muscarinic receptor antagonists good for?
People who cant take tablets
Motion sickness
Bowel obstruction
What are the side effects of hyoscine hydrobromide?
Sedation
Memory problems
Glaucoma
Dry mouth and constipation
How do H1 receptor antagonists work?
Act on vestibular nuclei
Inhibits histaminergic signals from the vestibular system to CTZ in medulla
What are H1 receptor antagonists good for?
Motion sickness Morning sickness (promethazine)
Who cannot use cyclizine?
Little old ladies and children
Name some H1 receptor antagonists
Cyclizine Levomepromazine Cinnirazine Promethazine Diphenhydramine
What are side effects of H1 receptor antagonists?
Sedation
Excitation
Dry mouth, constipation, urinalysis retention, cardiac toxicity
Which drugs act on visceral afferents in the gut?
5HT3 receptor antagonists
D2 receptor antagonists
How does 5HT3 receptor an antagonist work?
Peripherally - reduces GI motility, reduces GI secretions
Centrally - act to inhibit the CTZ
Name some 5HT3 receptor antagonists?
Ondansetron
Granisetron
Palonosetron
What are the side effects of 5HT3 receptor antagonists?
Uncommon Constipation Headache Elevated liver enzymes Long QT syndrome
Name some D2 receptor antagonists
Metoclopramide
Domperidone
What is the action of metoclopramide?
Increases acetylcholine at muscarinic receptors in the gut
Promotes gastric emptying
Increases peristalsis
What are the side effects of D2 receptor antagonists?
Galactorrhoea via prolactin release
Extra-pyramidal effects - dystonia, Parkinsonism
What is metoclopramide good for?
GORD
Ileus
What is domperidone good for?
Improving lactation in breastfeeding
What are the side effects of domperidone?
Sudden cardiac death - long QT and VT
Galactorrhoea
Which D2 receptor antagonists work on the CTZ?
Prochlorperazine
Chlorpromazine
Levomepromazine
Haloperidol
What is haloperidol good for?
Chemotherapy and palliation
What are corticosteroids good for?
Perioeprative nausea and vomiting
Chemotherapy
Palliation
Name 2 corticosteroids
Dexamethasone
Methylprednisolone
What are the side effects of corticosteroids?
Insomnia
Increased appetite
Increase blood sugar
Name a useful cannabinoid
Nabilone
What are the side effects of nabilone?
Dizziness
Drowsiness
Name some neurokinin 1 receptor antagonists
Aprepitant
Fosaprepitant
Netupitant
What is the action of neurokinin 1 receptor antagonists?
Prevent the action of substance P at CTZ and in peripheral nerves
Boosts effects of 5HT3 receptor antagonists
What are neurokinin 1 receptor antagonists good for?
Chemotherapy - particularly for delayed emesis
What are the side effects of neurokinin 1 receptor antagonists?
Headache
Diarrhoea/constipation
Stevens-Johnson syndrome
For gut problems, what is usually the order of drugs given?
Ondansetron and/or cyclizine
Then add dexamethasone
What is the treatment for hyperemesis Gravidarum?
Promethazine or prochlorperazine
Then add metoclopramide
Then add ondansetron
