Drugs that neutralize excess acid to relieve indigestion or help peptic ulcers to heal

Common drugs

  • Alginates

  • Aluminium hydroxide

  • Calcium carbonate

  • Magnesium hydroxide

  • Simeticone

  • Sodium bicarbonate

Antacids are used to relieve upper abdominal discomfort caused by irritation of the stomach or duodenum (see Indigestion). Antacids can also relieve the discomfort caused by gastro-oesophageal reflux disease, in which stomach acid is regurgitated into the oesophagus. They may help to ease symptoms due to peptic ulcers.

Antacid preparations may contain aluminium and/or magnesium salts, both of which neutralize stomach acid (see How antacids work). Some contain additional ingredients such as simeticone, which disperses bubbles of gas to reduce bloating, or alginates, which provide a protective coating for the oesophagus if regurgitation of the stomach contents occurs. If indigestion persists for more than a week, see your doctor.

What are the side effects?

Most antacid preparations have very few side effects. However, antacids containing aluminium can occasionally cause constipation, while those that contain magnesium may cause diarrhoea. The antacid sodium bicarbonate may produce excess gas in the stomach, which can cause abdominal bloating. Sodium bicarbonate may cause fluid retention in people who have kidney disease or chronic heart failure and should therefore be avoided by anyone with these conditions.

Consult your doctor before using ant-acids if you are already taking other medication; antacids can interfere with the body’s absorption of certain drugs.


You should not take antacids regularly, unless advised to do so by your doctor, because they may suppress the symptoms of a potentially serious disorder or provoke serious complications.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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