GI

H2 Receptor Blockers

Gastrointestinal

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Examples

famotidineranitidinecimetidine

Prefix / Suffix: -tidine

Physiology

Histamine binds to H2 receptors on parietal cells, stimulating gastric acid secretion.

Mechanism of Action

They block H2 receptors on gastric parietal cells, reducing acid production.

Indications

  • GERD
  • Peptic ulcer disease
  • Heartburn

Side Effects / Adverse Effects

  • Headache
  • Dizziness
  • Confusion (especially in elderly with cimetidine)
  • Gynecomastia (cimetidine — antiandrogen effect)

Contraindications

  • Hypersensitivity

Nursing Considerations

  • Give at bedtime if once daily (acid secretion peaks at night)
  • Monitor elderly for confusion (especially cimetidine)
  • Cimetidine has many drug interactions (inhibits CYP450)
  • Assess for symptom relief
  • Less potent than PPIs — may be used for milder cases

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Disclaimer: PharmPal Nurse is for education only and is not medical advice. Do not use it to diagnose, treat, prescribe, or make patient-care decisions; always verify with current drug references, your instructor, facility policy, and a licensed provider. In emergencies, call local emergency services.