H2RA

Question 1

H2-receptor antagonists - indications

Answer 1

Peptic ulcer disease (PUD)
(treatment + prevention)

GORD and dyspepsia (symptomatic relief)

Question 2

H2-receptor antagonists - examples

Answer 2

Ranitidine

Question 3

H2-receptor antagonists - MOA

Answer 3

Histamine is released by local paracrine cells and binds to H2 receptors on gastric parietal cells - this subsequently activates the proton pump to secrete acid

Histamine H2-receptor antagonists reduce gastric acid secretion by blocking the H2-receptors

note: however, the proton pump can also be stimulated by other pathways - therefore H2 receptor antagonists cannot COMPLETELY suppress gastric acid production (unlike PPIs which target the final stage of gastric acid production)

Question 4

H2-receptor antagonists - adverse effects

Answer 4

generally well tolerated - very few side effects

most common:

• bowel disturbances (diarrhoea + less often constipation)
• headache
• dizziness

Question 5

H2-receptor antagonists - cautions

Answer 5

H2RA are excreted by the kidneys - therefore dose should be reduced in patients with renal impairment

Can disguise symptoms of gastro-oesophageal cancer - therefore make sure to rule out first

Question 6

H2-receptor antagonists - interactions

Answer 6

NONE