Anti-emetics Flashcards
Which drugs act on the vestibular nuclei?
Muscarinic receptor antagonists
H1 receptor antagonists
What is an example of a muscarinic receptor antagonist?
Hyoscine hydrobromide
What are muscarinic receptor antagonists recommended for?
Motion sickness
People who can’t take tablets (patch)
Bowel obstruction
What are some side effects of muscarinic receptor antagonists?
Sedation
Memory problems
Glaucoma
Dry mouth and constipation
What are some examples of H1 receptor antagonists?
Cyclizine
Levomepromazine
Promethazine
How do H1 antagonists act as anti-emetics?
Inhibit histaminergic signals from the vestibular system to CTZ
What are H1 receptor antagonists used for (anti-emetic)?
Motion sickness - long plane journeys
What can cyclizine be used for?
Morning sickness
What are some side effects of H1 receptor antagonists?
Sedation
Excitation
Dry mouth, constipation, urinary retention
Cardiac toxicity - long QT syndrome
What are examples of 5HT3 receptor antagonists?
Ondansetron
Granesitron
Palonosetron
How do 5HT3 receptor antagonists act as anti-emetics?
Act on visceral afferents in the gut
Peripherally:
Reduce GI motility
Reduce GI secretions
Centrally:
Inhibit CTZ
Often 1st line treatment
What are some side effects of 5HT3 antagonists?
Constipation Headache Elevated liver enzymes Long QT syndrome Extra-pyramidal effects; dystonia, Parkinsonism
Side effects are uncommon
What are some D2 receptor antagonists?
Metacloperamide
Domperidone
How does metaclopramide (D2 receptor antagonist) act as an anti-emetic?
Increase AcH at muscarinic receptors in the gut
Promotes gastric emptying
Increase tone of lower oesophageal sphincter
Increase peristalsis
Decrease tone of pyloric sphincter
What are some side effects of metacloperamide?
Galactorrhoea
Extra-pyramidal effects; dystonia, Parkinsonism
What is domperidone good for? (Most an anti-emetic use)
Improving lactation in mothers
However used selectively bc can cause sudden cardiac death - long QT
What D2 receptor antagonists act on the CTZ?
Metacloperamide Domperidone Prochlorperazine Chlorpromazine Levomepromazine Haloperidol
What are D2 receptor antagonists used for?
Motion sickness, vertigo
Prochlorperazine used in pregnancy
What are some side effects of D2 receptor antagonists?
Extra-pyramidal effects; dystonia, Parkinsonism
Sedation
Hypotension
What corticosteroids are used as anti-emetics?
Dexamethasone
Methylprednisolone
How do corticosteroids act as anti-emetics?
Assumed to act on CTZ
May also have properties of D2 receptors
Used for peri-operative nausea and vomiting, chemo and palliation
How are cannabinoids used as anti-emetics?
Assumed to act on the CTZ
Last line for chemo
Side effects:
Dizziness, drowsiness
How do neurokinin-1 receptor antagonists act as anti-emetics?
Prevent action of substance P at CTZ and in peripheral nerves
Also boosts effects of 5HT3 receptor antagonists
Good for chemo, esp delayed emesis
How is motion sickness treated?
Prevention is better than cure
Hyoscine hydrobromide- 1st line
Selective, good for long plane journeys
Cinnirazine - fewer side effects
What are prokinetics? And what are they used for?
Increase peristalsis of the gut
Used for GORD, and paralytic ileus
Don’t use w/ bowel obstruction as there is a risk of perforation
What causes hyperemesis gravidarum? And what is the treatment?
Rapid rise in βhCG
1) promethazine or prochlorperazine
2) metacloperamide
3) ondansetron
What’s the order of anti-emetics used for chemo?
1) dexamethasone
2) dexamethasone and ondansetron
3) dexamethasone and ondansetron and aprepitant
What are some risk factors for post-op nausea and vomiting?
Female, younger age, non-smoker
GA, post-op opioids
Longer surgery
