Paper II
2021 May (Supplementary) (2010 Scheme)

Question

H2 blockers

Q63 marksShort Notes

Answer

Examples: Ranitidine, Famotidine, Cimetidine

Mechanism of action

  • Competitively block H2 receptors on gastric parietal cells, reducing histamine-stimulated gastric acid secretion

Uses

  • Peptic ulcer disease, GERD, prevention of stress ulcers

Adverse effects

  • Generally well tolerated
  • Cimetidine: gynaecomastia (antiandrogenic effect), significant CYP450 inhibition — multiple drug interactions
  • Ranitidine/famotidine: fewer interactions, better tolerated
  • Rare: confusion (especially in elderly)

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