Anti-emetics Flashcards
What are the general indications for anti-emetics?
Nausea and vomiting
What are the types of anti-emetics?
- H1 receptor antagonists
- 5-HT3 receptor antagonists
- D2 receptor antagonists
- Phenothiazines
- Hyoscine (anti-muscarinic)
What are some examples of H1 receptor antagonists?
- Cyclizine
- Promethiazine
How do H1 receptor antagonists act as anti-emetics?
Block histamine (H1) and acetylcholine receptors in the chemoreceptor trigger zone
What are some examples of 5-HT3 receptor antagonists?
Ondansetron
How does ondansetron exert its anti-emetic effects?
Unknown
What are some examples of D2 receptor antagonists?
- Metoclopramide
- Domperidone
How do D2 receptor antagonists act as anti-emetics?
Inhibit dopaminergic stimulation on the chemoreceptor trigger zone
What are some examples of phenothiazines?
- Prochlorperazine
- Chlorpromazine
How do phenothiazines act as anti-emetics?
Block a variety of receptors that stimulate the chemoreceptor trigger zone
How does hyoscine act as an anti-emetic?
Exerts a spasmolytic action on the smooth muscle of the gastrointestinal biliary and genitourinary tracts and has a peripheral anticholinergic effect on the visceral wall
What anti-emetic is best for drug-induced vomiting?
Cyclizine
What anti-emetic is best for vomiting in pregnancy?
Promethiazine
What anti-emetic is best post-operatively?
Hyoscine
What anti-emetic is used for obstruction?
Metoclopramide
What anti-emetic is best for motion sickness?
Hyoscine
How can anti-emetics be administered?
- PO
- IV
- IM
- PR
When should phenothiazines and dopamine receptor antagonists be avoided?
In Parkinson’s disease
Because of increased risk of extra-pyramidal side effects
When is domperidone contraindicated?
- In people with underlying cardiac or hepatic impairment
- In people on medications that inhibit CYP3A4
Due to cardiac side effects
What caution should be taken with metoclopramide?
Only use for up to 5 days
Why should metoclopramide only be used for up to 5 days?
It is associated with severe neurological adverse effects
What monitoring may be required for patients on 5HTs antagonists or phenothiazines?
ECG to look for prolonged QT
Can anti-emetics be used in combination?
Should be avoided
Which anti-emetics should metoclopramide not be prescribed alongside?
- Ondansetron
- Cyclizine
What anti-emetics should cyclizine not be prescribed alongside?
- Metoclopramide
- Domperidone
What medications can cyclizine interact with?
- Opioids (increases sedation)
- Anticholinergics
What medications does ondansetron interact with?
- SSRI’s
- Enhanced action when prescribed with steroids
What medications does metoclopramide interact with?
- Effect is reduced by opioids
What drugs can domperidone interact with?
Absorption can be reduced by antacids and H2 receptor antagonists
What drugs does hyoscine interact with?
This is in the muscarinic antagonist cards
What are the important side-effects of H1 receptor antagonists?
Drowsiness
What are the important side-effects of phenothiazines?
- Drowsiness
- Postural hypotension
- Prolonged QT interval
What are the important side-effects of muscarinic antagonists?
- Postural hypotension
- Dry mouth
What are the important side-effects of 5-HT3 receptor antagonists?
Prolonged QT interval
What are the important side-effects of D2 receptor antagonists?
Extrapyramidal side-effects
What anti-emetics can cause headache, constipation/diarrhoea?
Several types
What patient counselling should be given to patients on anti-emetics?
- Indication
- Side-effects and consequences
- Anti-emetic can be changed if no relief
What are the most important side-effects to warn patients about with anti-emetics?
- Postural hypotension
- Dizziness
- Extrapyramidal side-effects
What can be the consequences of anti-emetics causing dizziness and postural hypotension?
- Falls
- Unable to drive
- Unable to operate machinery
What are some extrapyramidal side-effects caused by D2 receptor antagonists?
- Tremor
- Bradykinesia
- Acute dystonia
- Akathasia
- Tardive dyskinesia
- Parkinsonism
What patient counselling is required with anti-emetics?
- Indication and side effects
- Impairment of function
- Extrapyramidal side effects
- Changing anti-emetic if no relief