H2 Receptor Antagonists

Question 1

Give 2 examples of H2 receptor antagonists?

Answer 1

• Ranitidine

- Cimetidine

Question 2

What is the action of H2 receptor antagonists?

Answer 2

Reduce gastric acid production by binding to H2 receptors and blocking them

Question 3

How are H2 receptor antagonists administered?

Answer 3

Oral

Question 4

What are the indications for H2 receptor antagonists?

Answer 4

• Peptic ulcers
• Duodenal ulcers
• GORD

Question 5

What are the cautions for the use of H2 receptor antagonists?

Answer 5

Renal impairment

Question 6

When should the dose of a H2 receptor antagonist be halved?

Answer 6

eGFR <50 ml/min

Question 7

What drugs can cimetidine interact with?

Answer 7

• Warfarin
• Phenytoin
• Theophylline
• Carbamazepine
• Sodium valproate
• Clopidogrel

Question 8

How does cimetidine interact with clopidogrel?

Answer 8

Reduces its antiplatelet effects

Question 9

How does cimetidine interact with warfarin, phenytoin, theophylline, carbamazepine and sodium valproate?

Answer 9

By inhibiting the CYP450 enzymes and reducing their metabolism

Question 10

What is the effect on the drugs metabolised by CYP450 enzymes of cimetidine?

Answer 10

Increases their effects

Question 11

When should investigations be undertaken before starting H2 receptor antagonists?

Answer 11

When suspicious symptoms for gastric cancer

Question 12

What are the commons side-effects of H2 receptor antagonists?

Answer 12

• Headache
• Dizziness
• Diarrhoea

Question 13

What are the less common side-effects of H2 receptor antagonists?

Answer 13

• Rashes
• Confusion
• Depression
• Bleeding disorders
• Gynaecomastia

Question 14

What mnemonic can be used to remember drugs that can cause gynaecomastia?

Answer 14

DISCO

Question 15

What does DISCO stand for?

Answer 15

• Digoxin
• Isoniazid
• Spironolactone
• Cimetidine
• Oestrogens

Question 16

What patients counselling should be given when prescribing H2 receptor antagonists?

Answer 16

• How to further reduce acidity

- Red flag symptoms of gastric cancer

Question 17

How can acidity be further reduced?

Answer 17

• Avoid foods and drinks that worsen symptoms

- Avoid lying flat after eating