• GORD (mild symptoms) or GORD in pregnancy
  • Symptomatic chronic peptic ulcer disease


  • Not recommended in children <12
  • Avoid antacids with large amounts of sodium in hepatic or renal failure with fluid retention and avoid antacids which cause constipation (mainly aluminium containing ones e.g. Aluminium Hydroxide (Co-magaldrox); also avoid antacids with magnesium salts if there is a risk of hepatorenal failure.
  • Avoid aluminium and magnesium salts in renal failure
  • Hypophosphataemia

Side effects/Interactions

  • Ideally, should not be taken at the same time as any other drugs as it can alter absorption
    • e.g. decrease the absorption of acidic drugs e.g. digoxin, phenytoin, chlorpromazine, isoniazid
      • NB Antacids have the ability to reduce the absorption of may more drugs- drugs should be taken either an hour before or 2 hours after taking antacids
    • e.g. increase the absorption of alkali drugs e.g. anticongestives (pseudoephrine e.g. sudafed); levodopa
    • Particularly affects absorption of calcium (not recommended for patients with osteoporosis taking calcium supplementation)
  • Common side effects include constipation (aluminium containing compounds) or diarrhoea (magnesium containing compounds)
    • Reason for not using in children (require high calcium intake for bone growth and can be linked with rickets)

Alginates e.g. Peptac (sodium alginate)

  • e.g. Gaviscon
  • Also used for GORD
  • Should be avoided where there is any signs of fluid retention or a salt-restriction diet is required (high sodium concentration)

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