Anti-Emetics Flashcards
Name the types of anti-emetics and where they act
D2 receptor antagonists - visceral afferents from the gut and CTZ
5HT3 receptor antagonists - visceral afferents from the gut and CTZ
Muscarinic receptor antagonists - vestibular nuclei and CTZ
H1 receptor antagonists - vestibular nuclei and CTZ
Corticosteroids - CTZ
Cannabinoids - CTZ
NK1 receptor antagonists - CTZ
What is the CTZ, where is it found and what stimulates it
CTZ - chemoreceptor trigger zone. Found within the medulla oblongata and stimulates vomiting. Inputs include:
Sensory afferents via midbrain
Direct triggers
Vestibular nuclei
Visceral afferents from gut
Name a muscarinic receptor antagonist
Hyoscine hydrobromide
How do muscarinic receptor antagonists work and what are they useful for
Muscarinic receptor antagonists competively block muscarinic ACh receptors in the vestibular nuclei and in the CTZ but will affect all mAChR in the body
Good for those who cannot take tablets, for motion sickness and bowel obstruction
Name some side effects of muscarinic receptor antagonists
Sedation
Memory problems
Glaucoma
Dry mouth
Constipation
Name some H1 receptor antagonists
Cyclizine - main one used
Levomepromazine
Cinnarizine
Promethazine - pregnancy
Diphenhydramine
How do H1 receptor antagonists work and name some uses
H1 receptor antagonists work by acting on the vestibular nuclei to inhibt H1 receptors. Also inhibit histaminergic signals from vestibular system to the CTZ
Uses include motion sickness and morning sickness
Name some side effects of H1 receptor antagonists
Sedation - more prominant in children and old ladies given cyclizine
Excitation
Antimuscarinic - dry mouth, constipation, retention
Cardiac toxicity (long QT)
Name some serotonin receptor antagonists
Ondansetron
Granesitron
Palonosetron
Describe how serotonin receptor antagonists work as an anti-emetic and when are they used
5HT receptor antagonists act peripherally to decrease GI motility and secretions. Also act centrally to inhibit the CTZ
Used as first line treatment in emesis
Name some side effects of serotonin receptor antagonists
Constipation
Headache
Elevated liver enzymes
Long QT
Extra-pyramidal effects - dystonia, parkinsonism
Name the D2 receptor antagonists
Metoclopramide
Domperidone
Chlorpromazine
Haloperidol
Describe how metoclopramide works and what it is used for
Metoclopramide increases ACh at muscarinic receptors in the gut to increase gastric emptying and increase peristalsis
It promotes gastric emptying by increasing tone at LOS, increasing tone and amplitude to gastric contractions and decreasing tone of pyloric sphincter
Good for GORD and ileus
What are the side effects of metoclopramide
Galactorrhoea
Extra-pyramidal effects - dystonia and parkinsonism
What are the uses and side effects of the D2 receptor antagonists, excluding metoclopramide and domperidone
Uses: motion sickness, vertigo, pregnancy
Haloperidol good for chemotherapy and palliation
Side effects include: extra-pyramidal effects (dystonia, parkinsonism), sedation, hypotension
Name some corticosteroids used as antiemetics
Dexamethasone
Methylprednisolone
Describe how corticosteroids act as antiemetics and when they are used
Corticosteriods act on the CTZ but may have properties of D2 receptor antagonists. Also have anti-inflammatory effects
Good for perioperative nausea and vomiting, chemotherapy, palliation (dexamethasone)
What are the side effects of corticosteriods
Insomnia
Increased appetite
Increased blood sugar
Name some neurokinin 1 receptor antagonists
Aprepitant
Fosaprepitant
Netupitant
Describe how neurokinin 1 receptor antagonists work and when they are used
Neurokinin 1 receptor antagonists prevent the action of substance P at CTZ and in peripheral nerves -> blocks vomiting and pain
Also boost effects of 5HT receptor antagonists
Good for chemotherapy in combination with other drugs
Name some side effects of neurokinin 1 receptor antagonists
Headache
Diarrhoea
Constipation
Stevens-Johnson syndrome
Which antiemetics are used in the treatment of motion sickness
Hyoscine hydrobromide as 1st line
Cinnarizine - fewer side ffects
What drugs are used in the treatment of emesis caused by gut problems
Prokinetics for GORD and ileus - domperidone and metoclopramide
Ondansetron and/or cyclizine and then add dexamethasone
Which drugs are given in the treatment of hyperemesis gravidarum
Promethazine or prochlorperazine
Then metoclopramide
Then ondansetron
Which drugs are given in the treatment of chemotherapy induced emesis
Low risk - dexamethasone
Moderate risk - dexamethasone and ondansetron
High risk - dexamethasone, ondansetron and aprepitant
Metoclopramide for rescue
