Nausea And Labyrinth Disorders Flashcards
What are the causes of nausea?
Drugs and toxic substances Labyrinthitis Vestibular disorders Motion sickness Gut irritation Higher stimuli
How does nausea and vomiting occur?
When the vomiting centre inside the brain is activated by input from the chemoreceptor trigger zone which contains dopamine, serotonin, histamine and muscarinic receptors
How do antiemetic work?
By antagonising the receptors in the chemoreceptor trigger zone
What are the dopamine antagonists that can be used for nausea?
Metoclopramide Domperidone Prochlorperazine Chlorpromazine Haloperidol, levomepromazine Droperidol
What are the antihistamines used for vertigo and motion sickness?
Cinnarizine
Cyclizine
Promethazine teoclate
What are the antimuscarinics used for motion sickness?
Hyoscine hydrobromide
What are the 5-HT3 antagonists used in chemotherapy or post operative nausea and vomiting?
Granisetron
Ondansetron
Palonosetron
What are the other antiemetics used in nausea?
Dexamethasone - chemotherapy, post operative
Nabilone - synthetic cannabinoid, used in chemo unresponsive to other anti emetics
Aprepitant - chemotherapy. + dexamethasone, 5HT3 antagonist
What do you use for mild nausea in the first trimester of pregnancy?
Nothing
What do you use for severe vomiting and nausea in the first trimester of pregnancy?
Promethazine
Prochlorperazine
Metoclopramide
What do you use for preventative post operative nausea and vomiting?
5HT3 receptor antagonists, droperidol, dexamethasone, phenothiazine, cyclizine
What do you use for high risk patients for post operative nausea and vomiting?
Combination of two or more antiemetics from different classes
What is the mechanism of action of metoclopramide?
Antagonises D2 receptors in chemoreceptor trigger zone
Also acts directly on gut to promote gastric emptying - prokinetic effect
What is the MHRA warning for metoclopramide?
Risk of neurological adverse effects - restricted dose and duration of use
What is the maximum dose of metoclopramide?
18+
5 days
10mg TDS
What is metoclopramide used for?
Prevention of nausea and vomiting
Symptomatic treatment of nausea and vomiting
What are the side effects of metoclopramide?
Acute dystonic reactions
Procyclidine aborts dystonic attacks
What are the interactions of metoclopramide?
Antipsychotics- increase extrapyramidal side effects
Parkinson’s disease - exacerbates condition
What is the mechanism of action of domperidone?
Antagonised D2 receptors in chemoreceptor trigger zone
Also acts directly on gut to promote gastric emptying - prokinetic effect
What is the MHRA advice for domperidone?
Risk of cardiac side effects - restricted indication, new contraindications, reduced dose and duration
What is the maximum dose for domperidone?
1 week
10mg TDS
Adult 12+ and over 35kg
What is domperidone used for?
Symptomatic relief of nausea and vomiting
Choice antiemetic in Parkinson’s disease
What are the cardiac side effects of domperidone?
QT prolongation
Ventricular arrhythmias
Sudden death
What are the counselling points for domperidone?
Report signs of arrhythmias
What are the contraindications of domperidone?
Impaired cardiac conduction
Cardiac disease
Severe liver impairment
What are the interactions of domperidone?
Potent CYP34 inhibitor - amiodarone, ketoconazole, erythromycin
Drugs causing QT prolongation - amiodarone, SSRIs, quinolones
What is the mechanism of action of 5HT3 receptor antagonists?
Blocks HT3 receptors in the chemoreceptor trigger zone and GI tract
5HT is a key neurotransmitter released by the gut in response to emetogenic stimuli
What are the 5HT3 receptor antagonists?
Granisetron
Ondansetron
Palonosetron - only for chemo
What are granisetron and ondansetron used for?
Post operative nausea and vomiting
Chemotherapy induced nausea and vomiting
What are the side effects of 5HT3 receptor antagonists?
QT interval prolongation
What are the interactions of the 5HT3 antagonists that increase the risk of torsades de pointes with hypokalaemia?
Loop/thiazide diuretics Corticosteroids Beta agonist - salbutamol, theophylline Stimulant laxatives abuse Amphotericin B
What are the interactions of the 5HT3 antagonists that increase the risk of QT interval prolongation?
Amiodarone Clarithromycin Quinine Sumatriptan Lithium Antipsychotics
What are the interactions of the 5HT3 antagonists that increase the risk of serotonin syndrome?
5HT1a agonists
Sumatriptan
MAOIs
SSRIs