Anti-emetics Flashcards by Ella Knight

What are the main classes of anti-emetics?

H1 receptor antagonist
D2 receptor antagonist
5HT3 receptor antagonist 
Muscarinic receptor antagonist
Neurokinin-1 antagonist

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What is the part of the brain that triggers vomiting?

Chemoreceptor trigger zone (CTZ)

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What are the triggers for the CTZ?

Sensory afferents
Direct triggers (drugs/toxins)
Vestibular nuclei
Visceral afferents from gut

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What classes act on the vestibular nuclei?

Muscarinic receptor antagonist

H1 receptor antagonist

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What classes act on the gut?

5HT3 receptor antagonists

D2 receptor antagonists

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What classes act on the CTZ?

D2 receptor antagonist
5HT3 receptor antagonist 
Muscarinic receptor antagonist
H1 receptor antagonist
Neurokinin-1 receptor antagonist

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What is an example of a muscarinic receptor antagonist?

Hyoscine hydrobromide

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What is the mechanism of muscarinic receptor antagonist?

Blocks muscarinic ACh receptors - competitive inhibitor

vestibular nuclei
CTZ

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What is hyoscine hydrobromide used for?

People who cant take tablets
Motion sickness
Bowel obstruction

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What are the routes for hyoscine hydrobromide?

Patch
Oral
Subcutaneous

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What are the side effects of hyoscine hydrobromide?

Sedation 
Memory problems
Glaucoma 
Dry mouth 
Constipation

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What are examples of H1 receptor antagonists?

Cyclizine

Promethazine

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What is the mechanism of H1 receptor antagonists?

Inhibits histaminergic signals from vestibular system to CTZ

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What is Cyclizine used for?

Nausea + Vomiting

Motion sickness

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What are the routes of administration for Cyclizine?

Oral
IV
IM

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Who is Cyclizine not ideal for?

Small old ladies
Children

Side effects are worse

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What is promethazine used for?

Motion sickness

Morning sickness

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What are the side effects of H1 receptor antagonists?

Sedation 
Excitation 
Dry mouth 
Constipation 
Cardiac toxicity (long QT)

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What classes act on visceral afferents in the gut?

5HT3 receptor antagonist

D2 receptor antagonist

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What is 5HT also known as?

Serotonin

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What is the effect of serotonin in the gut?

Excites enteric neurones

smooth muscle contraction
increases gut secretions

Regulates appetite

What is an example of a 5HT3 receptor antagonist?

Ondansetron

What is the mechanism of ondansetron?

Peripherally

reduces GI motility
reduces GI secretions

Centrally
- inhibits CTZ

What is ondansetron used for?

Chemo nausea

Post-operative nausea

What are the routes of administration for ondansetron?

Oral PR IM

What are the side effects of ondansetron?

Constipation Headache Elevated liver enzymes Long QT syndrome

What are examples of D2 receptor antagonists that act in the gut?

Metoclopramide | Domperidone

What is the mechanism of action for metoclopramide?

Increases ACh at muscarinic receptors in the gut - promotes gastric emptying - increases tone at LOS - decreases tone of pylorus - increases peristalsis

What is metoclopramide used for?

Nausea GORD Ileus

What are routes of administration of metoclopramide?

PO IM SC

What are the side effects of metoclopramide?

Galactorrhoea | Extra-pyramidal effects

What is the mechanism of domperidone?

Increases ACh at muscarinic receptors in the gut - promotes gastric emptying - increases tone at LOS - decreases tone of pylorus - increases peristalsis

What is domperidone used for?

Nausea

What is the route of administration for domperidone?

Oral

What are the side effects of domperidone?

Sudden cardiac death (long QT + VT) | Galactorrhoea

What classes act on the CTZ?

5HT3 receptor antagonists H1 receptor antagonists Muscarininc receptor D2 receptor antagonist

What are examples of D2 receptor antagonists that act on the CTZ?

Prochlorperazine Chlorpromazine Haloperidol

What is chlorpromazine used for?

Motion sickness | Vertigo

When is prochlorperazine used for?

Pregnancy

What is haloperidol used for?

Nausea Chemo/palliation Schizophrenia Delirium

What are side effects of D2 receptor antagonists?

Extra-pyramidal effects - dystonia - parkinsonism Sedation Hypotension

What are examples of neurokinin-1 receptor antagonists?

Aprepitant | Fosaprepitant

What is the mechanism of action of neurokinin-1 receptor antagonists?

Prevents the action of substance P at the CTZ + peripheral nerves Boosts effects of 5HT3 receptor antagonists

What are neurokinin-1 receptor antagonists used for?

Chemo nausea

What are the side effects of neurokinin-1 receptor antagonists?

Headache Diarrhoea Stevens-Johnson syndrome

What is Stevens-Johnson syndrome?

Type of severe skin reaction

What is the first line treatment for motion sickness?

Hyoscine hydrobromide

Which anti-emetics are prokinetics?

Domperidone | Metoclopramide

What are prokinetics used for?

GORD | Ileus

When should you not use prokinetics?

Obstruction | Risk of perforation

What are the anti-emetics used in bowel obstruction?

Ondansetron | Cyclizine

Which anti-emetics are used in hyperemesis gravidarum?

Promethazine OR prochlorperazine then add - metoclopramide then add - ondansetron