Anti-emetics

Question 1

Ondansetron

• Class
• MoA
• Indications
• Contraindications
• Side effects
• Pregnancy

Answer 1

Class:
5HT3 receptor anatagonist

MoA:
Blocks serotonin receptors in the gastrointestinal tract and CNS

Indications:
Acute gastroenteritis, post operative nausea, chemo/radiotherapy nausea

Contraindications:
Congenital long QT syndrome

Side effects:
Constipation, long QT

Pregnancy:
Avoid in first trimester

Question 2

Metoclopramide

• Class
• MoA
• Indications
• Contraindications

Answer 2

Class:
Dopamine receptor 2 antagonist

MoA:
Increases gastric emptying by promoting motility

Indications:
GORD, gastric paresis, vomiting

Contraindications:
Epilepsy, phaeocytochroma, post gastrointestinal surgery/haemorrhage/obstruction/perforation

Side effects:
Extra-pyramidal symptoms, tardive dyskinesia, diarrhoea, hyperprolactinemia, parkinsonism

Extra info:
Dystonic side effects more common in young females

Question 3

Cyclizine

• Class
• MoA
• Indications
• Contraindications
• Side effects

Answer 3

Class:
Antihistamines

MoA:
H1 receptor antagonist. Reduces labyrinth excitability and vestibular stimulation

Indications:
Cranial causes of nausea e.g. raised ICP, vestibular causes e.g. labyrinth disorders, serosal/visceral causes e.g. oral candidiasis, constipation

Contraindications:
Acute porphyria

Side-effects:
Agitation, glaucoma, depression