5. Nausea and labyrinth disorders Flashcards
List of antiemetics
Dopamine-receptor antagonist
domperidone
metoclopramide
Antihistamines
cinnarizine
cyclizine
promethazine
5-HT3 receptor antagonist
ondansetron
Antimuscarinic
hyoscine
Antipsychotics
Prochlorperazine
Droperidol
Haloperidol
Chemoreceptor trigger zone is outside the blood brain barrier
Antiemetics and pregnancy
Morning sickness usually common in 1st trimester. Recommend rest, change diet, drink fluids.
If symptoms persist:
antiemetic should be offered e.g promethazine, metoclopramide, prochlorperazine
Switch to a different class, if symptoms last longer than 24 hrs.
Seek specialist opinion, if symptoms last longer than 48 hours.
Treatment of post-operative nausea and vomiting
antiemetic combination therapy
combination of 2 or more antiemetics from different drug classes;
- dexamethasone
- domperidone
- prochlorperazine, droperdol, haloperido
- cyclizine
Before operation, an assesement is conducted for those at high risk for post-operative nausea and vomiting. Who are those groups?
- Female
- Non-smoker
- History
- Motion sickness
- Opioids
- Anaesthetic
- Surgery type
- Surgery Duration
Metoclopramide mechanism of action
A dopamine receptor antagonist and blocks D2 receptors in the chemoreceptor trigger zone.
Blocks dopamine receptors in the gut and promotes gastric emptying
Metoclopramide dose
10mg TDS for 5 days
Licensed for 18 years+
metoclopramide side effects
Acute dystonic reactions
- uncontrolled movements in the face, skeletal muscles and eyes
Metoclopramide enters the brain to cause this side effect
Common in young females/elderly
As metoclopramide blocks D2 receptors in the brain which regulates movem
As metoclopramide blocks D2 receptors in the brain which regulates movement. The same happens for antipsychotics.
Metoclopramide interactions
Increased risk of extrapyramidal symptoms if taken at the same time as antipsychotics
Metoclopramide should never ben given to a patient with Parkinson’s disease, as this antagonises their treatment.
Domperidone mechanism of action
works similarly to metoclopramide. It blocks dopamine-2, dopamine-3 receptors in the chemoreceptor trigger zone and in the gut
Domperidone and parkinson’s disease
Domperidone can be used in parkinson’s disease, as it does not cause extrapyrimidal symptoms due it not entering the brain
Domperidone dose
10mg TDS for 1 weeks
Licensed for 12 years
Lack of efficacy in those less than 12 years or those who weigh less than 35kg
Domperidone side effects
Can prolong QT interval.
Patients must report signs of fainting, palpitations.
Domperidone interactions
Interacts with drugs that also prolong the QT interval –> arrhythmias
Antipsychotic, anti-arrhythmic drugs, citalopram, escitalopram, clarithromycin, erythromycin, hydroxyzine, lithium, methadone, quinolones, onadensetron
Domperidone is metabolised by CYP3A4 enzymes. Therefore it interacts with CYP3Z4 inhibitors:
amiodarone, azole antinfungals: fluconaozle, ketoconazole, clarithromycin, erythromycin, diltiazem and verapamil
5-HT3 receptor antagonists mechanism of action
Blocks 5-HT3 receptors in the chemoreceptor trigger zone and GI tract
5-HT3 receptor antagonists side effect
Prolonged QT interval
5-HT3 receptor antagonists and pregnancy
Teratogenic
Increased risk of cleft lip, when used in the first trimester
5-HT3 receptor antagonists interactions
Interacts with drugs that also prolong the QT interval = arrhythmias
Antipsychotic, anti-arrhythmic drugs (amiodarone, sotalol) clomipramine, citalopram, escitalopram, clarithromycin, erythromcyin, domperidone, hydroxzine, lithoum, methadone, quinolones
Hypokalaemia increases the risk of a prolonged QT interval, therefore domperidone interacts with drugs that cause hypokalaemia:
beta agonists, corticosteroids, loop and thiazide diuretics, theophylline
Hypokalaemic drugs taken with drugs that prolong QT interval = increases risk of torsades de pointes
5-HT3 drugs are serotonergic (even tho they are antagonist, no clear reason)
Interacts with drugs that also increase serotonin = increasing risk of serotonin syndrome
antidepressants (TCA’s SSRI’s MAOI), amfetamine, lithium, MAO-B inhibitor, methadone, ST john’s wort, tramadol 5-HT1 agonists e.g sumatriptan
