Pharmacology

Question 1

Promethazine

Answer 1

• Class: anti-emetic.
• MOA: H1 receptor antagonist.
• Indication: pregnancy related N+V (1st line).
• Adverse effects/contraindications: drowsiness, dry throat and mouth (anticholinergic effects). Avoid in hepatic encephalopathy (sedating) and BPH (may cause urinary retention).

Question 2

Cyclizine

Answer 2

• Class: anti-emetic.
• MOA: H1 receptor antagonist.
• Indication: pregnancy related N+V (1st line).
• Adverse effects/contraindications: drowsiness, dry throat and mouth (anticholinergic effects). Avoid in hepatic encephalopathy (sedating) and BPH (may cause urinary retention).

Question 3

Metoclopramide

Answer 3

• Class: anti-emetic.
• MOA: D2 receptor antagonist.
• Indication: pregnancy related N+V (2nd line).
• Adverse effects/contraindications: diarrhoea, EPSE (e.g. acute dystonic reaction). Only prescribe for maximum of 5 days. Avoid in neonates, children and young adults, in intestinal obstruction (promotes relaxation and gastric emptying) and Parkinson’s disease.

Question 4

Ondansetron

Answer 4

• Class: anti-emetic.
• MOA: 5-HT3 receptor antagonist.
• Indication: pregnancy related N+V (2nd line).
• Adverse effects/contraindications: rarely side effects occur. Avoid in patients with prolonged QT interval.