Antiemetics – Histamine H1 receptor antagonists

Question 1

What are the generic and brand names for H1 receptor antagonists?

Answer 1

• Cyclizine (Migril)

Question 2

What is the method of action of H1 receptor antagonists?

Answer 2

• Blocks H1 receptors which are in the vomiting center of the brain
• Vomiting centre communicates with the vestibular system (hence why helpful in motion sickness/vertigo)

Question 3

What are the indications for H1 receptor antagonists?

Answer 3

• Prophylaxis of nausea and vomiting
• Treatment of nausea and vomiting
• In relation to motion sickness and vertigo

Question 4

What are the contraindications for H1 receptor antagonists?

Answer 4

• High risk of hepatic encephalopathy – due to drowsiness

* Patients susceptible to anticholinergic side effects e.g. prostatic hypertrophy

Question 5

What are the side effects of H1 receptor antagonists?

Answer 5

• Drowsiness
• Dry throat/mouth
Tachycardia/palpitations – if injected

Question 6

What are the interactions of H1 receptor antagonists?

Answer 6

• Sedative drugs – may increase their effect

* Ipratropium/tiotropium – may increase anticholinergic effect

Question 7

What information should be given to patients taking H1 receptor antagonists?

Answer 7

• Tell patients to be aware that this medication may make them drowsy
• Driving should be avoided