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Zantac Patient Tips

Medically reviewed by C. Fookes, BPharm. Last updated on Aug 28, 2018.

How it works

  • Zantac is a brand (trade) name for ranitidine. Ranitidine blocks the effect of histamine on histamine H2-receptors attached to the parietal cells (gastric acid-producing cells) lining the stomach.
  • Histamine stimulates the parietal cells to release stomach acid. By blocking H2 receptors, ranitidine prevents histamine from having this effect.
  • Zantac belongs to a class of medicines called H2 blockers, or histmine-2 blockers. It may also be called an acid suppressant.


  • Used for the short-term treatment of active duodenal or gastric ulcers.
  • May be used for up to 1 year for the maintenance treatment of healed duodenal or gastric ulcers.
  • Reduces stomach acid secretions so may be used in the treatment of gastroesophageal reflux disease (GERD) or hypersecretory conditions such as Zollinger-Ellison syndrome or systemic mastocytosis.
  • May also be used in the treatment and maintenance of endoscopically diagnosed erosive esophagitis.
  • May be used in addition to antacids.


If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • A headache and gastrointestinal side effects (such as constipation, diarrhea, nausea, abdominal pain). Other side effects are rare.
  • May cause false-positive results on urine protein tests.
  • A response to Zantac does not preclude gastric or duodenal malignancy (cancer). Endoscopy is the only way to do this.
  • The dosage of Zantac should be adjusted in people with kidney disease, and be considered in those with liver disease.
  • Avoid in people with acute porphyria (a group of disorders characterized by a build-up of porphyrin-producing natural chemicals).
  • May interact with some other medications including warfarin, HIV antivirals, procainamide, and benzodiazepines.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

Bottom Line

Zantac is an acid-suppressing agent that may be used to treat a wide range of gastric-acid related disorders, including gastric ulcers and GERD. A headache is the most common side effect.


  • May be taken with or without food.
  • Usually taken twice daily when used to heal ulcers or treat GERD, but may be taken as a single daily dose at night time. Talk to your doctor about the most convenient dosing for you.
  • Antacids may be used when needed with Zantac for the relief of gastric acid-associated pain.

Response and Effectiveness

  • Peak effects are reached two to three hours after taking a 150mg dose. Symptom relief is usually experienced within two to 24 hours of starting Zantac.


Zantac (ranitidine) [Package Insert]. Revised 06/2018. GlaxoSmithKline LLC

  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Zantac only for the indication prescribed.

Copyright 1996-2018 Revision Date: 2018-08-28 01:40:31

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.