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