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LOSEC - a patient's guide


Losec is a drug used to treat stomach ulcers and gastric reflux. This article profiles the medication and its side effects.

DRUG NAME: omeprazole

USE: Antiulcerant

Losec is used for the treatment of stomach ulcers, gastro-oesophageal reflux disease (GORD) and Zollinger-Ellison syndrome (A rare condition with very high stomach acid). It is also prescribed for NSAID-associated (e.g. aspirin) ulceration, and during general anaesthesia to prevent acid aspiration.

This medicine is known as a proton pump inhibitor which blocks excess stomach acid production via a unique mechanism ( H+,K+-ATPase). By controlling the production of excess acid it allows the eroded lining of the stomach or oesophagus to heal due to the agent's long duration of action and high potency.


  • Gastric cancer
  • Liver disease
  • Pregnancy and breastfeeding

Side effects:

  • headache, dizziness
  • stomach upset/pain
  • constipation
  • rash
  • blurred vision
  • depression
  • dry mouth
  • muscle and joint pain


This medicine inhibits the metabolism of diazepam, phenytoin, warfarin (monitor).

Patient information:

  • Follow instructions carefully on the label of this medicine or as directed by your doctor.
  • Take this medicine regularly for it to work effectively (approximately 4 days until maximum effect).
  • Avoid smoking and eating certain foods (talk to your pharmacist).
  • Food: Taken after if this medicine upsets your stomach
  • Alcohol: May aggravate ulcer so best avoided
  • Swallow capsule whole or open capsule and mix contents with fruit juice or yoghurt.
  • Contact your doctor or seek urgent medical help if side effects are severe or ongoing.

See also:

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