Gastrointestinal
H2-receptor antagonists
H2 blockers (e.g. famotidine) — Acid-reducing drugs for heartburn and ulcers — a gentler step than PPIs in some situations.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
H2-receptor antagonists reduce stomach acid and are used for heartburn, acid reflux and peptic ulcers. They are a step down in potency from proton pump inhibitors but suit many milder cases.
How it works
They block histamine H2 receptors on the acid-producing cells of the stomach lining, reducing acid secretion — particularly the acid released overnight.
In practice
In practice H2 blockers are a useful option for milder reflux and indigestion, as a night-time add-on to a PPI for breakthrough symptoms, and where a PPI is unsuitable. They are generally well tolerated; the main practical points are a modest dose reduction in significant renal impairment and remembering that, like any acid suppression, they can mask the symptoms of a more serious upper-GI problem — so persistent or alarm symptoms still need investigation rather than indefinite treatment.
Examples
Practical use
How to take it & use it well
- Take it as directed, often once daily; if used for night-time symptoms it is commonly taken in the evening.
- It can be taken with or without food, so fit it around your routine.
- For occasional heartburn it can be used as needed, while ongoing conditions may need a regular course.
- If symptoms persist despite treatment, or you have difficulty swallowing or unexplained weight loss, see your GP.
- Tell your pharmacist if you are buying it over the counter and already take other stomach or prescription medicines.
Common uses
- Heartburn and acid reflux
- Peptic ulcer disease
- Night-time acid breakthrough alongside a PPI
Monitoring
- Symptom response
- Renal function where relevant
- Review for alarm features (weight loss, swallowing difficulty, bleeding)
Weighing it up
Advantages & disadvantages
Advantages
- It reduces stomach acid and eases heartburn and indigestion.
- It can be useful for night-time acid symptoms.
- It is generally well tolerated with few side effects.
- It offers an alternative for people who do not get on with proton pump inhibitors.
Disadvantages
- It is usually less powerful at suppressing acid than a proton pump inhibitor.
- Its effect can lessen over time with continuous use.
- Occasional side effects include headache, dizziness or bowel changes.
- Doses may need adjusting in people with reduced kidney function.
Key safety principles
What to watch for
- Generally well tolerated; reduce the dose in significant renal impairment.
- Cimetidine interacts with several drugs via liver enzymes (other H2 blockers far less so).
- Can mask the symptoms of more serious stomach disease — investigate alarm or persistent symptoms.
Key interactions
What to avoid or check alongside
- By reducing stomach acid, it can lower the absorption of some medicines that need acid, such as certain antifungals like itraconazole.
- It may affect the absorption of some HIV medicines that depend on stomach acidity.
- It can alter how some other medicines are handled by the body, so check with a pharmacist when combining treatments.
- Spacing it from medicines whose absorption is acid-dependent can help maintain their effect.
Patient & carer advice
- See us if symptoms persist despite treatment, or if you notice weight loss, difficulty swallowing or dark stools
- These can be taken to prevent predictable night-time symptoms
- Lifestyle measures (weight, late meals, alcohol) help as well
Use with
Related clinical calculators
Dose and risk decisions for this class often depend on renal function, weight or bleeding/stroke risk. These tools help:
Answers
H2-receptor antagonists: frequently asked questions
What do H2-receptor antagonists do?
They reduce the amount of acid the stomach makes, which eases heartburn, indigestion and related conditions such as acid reflux.
Are H2 antagonists as strong as proton pump inhibitors?
Usually they are less powerful at suppressing acid than proton pump inhibitors, though they can still be effective and are sometimes preferred for milder or night-time symptoms.
Can I take an H2 antagonist long term?
Some people use them regularly under guidance, but the acid-lowering effect can lessen over time. If you need them often or for long periods, see your GP to review the cause.
When should heartburn be checked by a doctor?
See your GP if symptoms persist despite treatment, or if you have difficulty or pain swallowing, unexplained weight loss, vomiting or black stools.
Can I take an H2 antagonist with other medicines?
Often yes, but because they reduce stomach acid they can affect how some medicines are absorbed. Check with a pharmacist, especially with certain antifungals or HIV medicines.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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