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H2 ANTAGONISTS - a patient's guide


H2 Antagonists are used in the treatment of stomach ulcers and heart burn. This article profiles the drugs' properties and possible side effects.


  • Cimetidine: Apo-Cimetidine, Duomet, Tagamet
  • Famotidine: Apo-Famotidine, Famox, Pepzan, Pepcidine
  • Nizatidine: Axid
  • Ranitidine: Zantac

USE: Histamine H2- receptor antagonist

H2- Antagonists are used for the treatment of stomach and duodenal ulcers, heartburn, and other related conditions which are a result of excess stomach acid production. They can also be used in post-op surgery to prevent stress ulcers in ill patients and in patients receiving NSAID (e.g. aspirin) therapy.

These medicines work by controlling the production of stomach acid via H2- receptor blockade, where they still allow the stomach to produce the amount of acid for digestion, but extra acid build-up that can cause problems (e.g. ulcers) does not occur.


Gastric cancer (these drugs may mask early symptoms of more serious disease)

Kidney impairment

Pregnancy and breastfeeding (discuss with doctor)

Side effects:

Occasional: headache, dizziness, diarrhoea, altered liver function tests

Rarely: acute stomach pain, slow heartbeat, confusion, depression, skin rash, blood disorders


Cimetidine is a potent enzyme inhibitor therefore should be avoided with warfarin, phenytoin, theophylline, anti-arrhythmics, antidepressants, opoid analgesics, and many other drugs.

Always check and discuss potential interactions with your doctor.

Famotidine, nizatidine and ranitidine do not have these interactions.

Patient information:

  • Follow instructions carefully on the label of this medicine or as directed by your doctor.
  • Used for the treatment of stomach ulcers therefore it should be taken regularly.
  • Avoid smoking and certain foods (talk to your pharmacist).
  • Food: Take with food if this medicine upsets your stomach
  • Alcohol: May aggravate stomach ulcers so best avoided
  • Contact your doctor or seek medical help if side effects are severe or ongoing.
  • These medications should not be taken long term without an accurate diagnosis of what is wrong - this may include endoscopy to look at the oesophagus, stomach and duodenum.

See also:

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