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H2 Receptor Antagonist — Aspiration Prophylaxis

Ranitidine / Famotidine (H2 Antagonist — Aspiration Prophylaxis)

Brand names: Famotidine (generic), Pepcid

Famotidine is an H2-receptor antagonist used perioperatively to reduce gastric acidity as aspiration prophylaxis (ranitidine has been withdrawn from UK use).

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It competitively blocks histamine H2 receptors on gastric parietal cells, reducing the volume and acidity of gastric secretions.

Prescribing in practice

  • Ranitidine was withdrawn from the UK market over nitrosamine (NDMA) contamination, so famotidine or an alternative is used in current practice.
  • Reducing gastric acidity and volume before anaesthesia aims to lessen the consequences of aspiration in at-risk patients.
  • Dose adjustment may be needed in significant renal impairment; consult current prescribing references.

Monitoring

Routine monitoring is not generally required for short perioperative use; assess renal function where relevant.

Counselling the patient

  • This medicine reduces stomach acid before your operation.
  • Mention any kidney problems or other medicines you take.

Evidence & guidelines

H2-receptor antagonists are established for aspiration prophylaxis, and the MHRA withdrawal of ranitidine reflects the NDMA contamination concern.

Reference: MHRA Ranitidine Withdrawal 2019; AAGBI Preoperative Assessment Guidelines; Mendelson (1946) aspiration criteria; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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