Antiemetics – Dopamine D2 receptor antagonists

Question 1

What are the generic and brand names for D2 receptor antagonists?

Answer 1

• Metoclopramide (Maxolon)
• Domperidone (Motilium)
• Prochlorperazine (Buccastem)

Question 2

What is the method of action of D2 receptor antagonists?

Answer 2

• Reduced gut motility/accelerates gastric emptying
• The main area of the brain that senses ‘sick making’ substances (chemoreceptor trigger zone) had D2 receptors which are blocked – reducing the sensation of sickness
• Enhances effect of dopamine on the gut – promoting relaxation of the stomach and oesophageal sphincter

Question 3

What are the indications for D2 receptor antagonists?

Answer 3

• Prophylaxis of nausea and vomiting

* Treatment of nausea and vomiting

Question 4

What are the contraindications for D2 receptor antagonists?

Answer 4

• Children/young adults – increased risk of extrapyramidal syndromes
• GI obstruction/perforation

Question 5

What are the side effects for D2 receptor antagonists?

Answer 5

• Diarrhoea

* Extrapyramidal syndromes (movement abnormalities) – more common in children/young adults

Question 6

What are the interactions for D2 receptor antagonists?

Answer 6

• Antipsychotics – risk of extrapyramidal syndromes increase

* Dopaminergic agents for Parkinson disease – will counteract their effect

Question 7

What is the main organ involved in the elimination of D2 receptor antagonists?

Answer 7

• Mainly kidney

Question 8

What patient information should be given to a patient taking D2 receptor antagonists?

Answer 8

• Explain the chance of abnormal movements and to seek medical attention if this happens