Antacids: What They Do, Medicines
Antacids are medicines that neutralise stomach acid to relieve indigestion and heartburn. They act within minutes but the effect lasts only a few hours. Common examples are aluminium hydroxide, magnesium hydroxide, calcium carbonate and sodium bicarbonate. See a doctor if you need them regularly.
Pharmacist review in progress. This page is based on the sources listed below and is being checked by our registered pharmacist.
How do Antacids work?
Antacids are weak bases. They react with the acid already in the stomach and turn it into water and salts, which makes the stomach contents less acidic.
Active ingredients of this type
These active ingredients belong to Antacids. They are listed A to Z.
- Aluminium hydroxide: Aluminium hydroxide is an antacid, a medicine that neutralises stomach acid.
- Citric acid: Citric acid is a mild food acid found in citrus fruit.
- Magnesium hydroxide: Magnesium hydroxide is an antacid, a medicine that neutralises stomach acid.
- Sodium bicarbonate: Sodium bicarbonate is an antacid, a medicine that quickly neutralises stomach acid.
Common questions
How long does an antacid last?
The effect lasts only a few hours, so symptoms can come back and repeat doses may be needed. If you need an antacid most days, or symptoms last more than 2 weeks, see a doctor instead of increasing the use.
Can antacids affect other medicines?
Yes. Antacids can change how well other medicines are absorbed. The NHS advises leaving a gap of 2 to 4 hours between an antacid and other medicines. Ask a pharmacist if you take prescription medicines.
Sources
- Antacids. NHS (UK)
- Antacid (aluminum hydroxide, magnesium hydroxide, simethicone) oral suspension: OTC drug label (revised 1/2016). DailyMed, US National Library of Medicine
- ATC/DDD Index: A02A antacids. WHO Collaborating Centre for Drug Statistics Methodology