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Zantac: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Nov 4, 2021.

1. 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 histamine-2 blockers. It may also be called an acid suppressant.
  • Zantac was withdrawn from the U.S. market in 2020.

2. Upsides

  • 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.

3. Downsides

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.
  • In early 2020, the FDA requested the removal of all ranitidine products (including Zantac) from the market. This was because a contaminant known as N-Nitrosodimethylamine (NDMA) has been found in ranitidine medications. This contaminant increases over time and when ranitidine is stored at higher than room temperature. NDMA is a probable human carcinogen (a substance that could cause cancer).
  • Research has not indicated any harm to the fetus in pregnant women administered Zantac; however, no controlled studies have been done. Zantac is secreted into breast milk. Only administer if the benefits outweigh the risks.

Note: 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. View complete list of side effects

4. 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.

5. Tips

  • 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.
  • Tell your doctor if you are pregnant, intending to become pregnant, or breastfeeding because Zantac may not be suitable for you.

6. 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.

7. Interactions

Medicines that interact with Zantac may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with Zantac. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with Zantac include:

  • anticoagulants (blood thinners), such as warfarin, or other drugs that have blood-thinning effects such as aspirin or NSAIDs
  • antifungals, such as fluconazole, itraconazole, ketoconazole, or voriconazole
  • cancer treatments, such as bosutinib, dabrafenib, dasatinib, erlotinib, neratinib, or pazopanib
  • epilepsy medications, such as carbamazepine, fosphenytoin, phenobarbital, or phenytoin
  • fentanyl
  • hepatitis medications, such as boceprevir, ledipasvir, sofosbuvir, and telaprevir
  • HIV medications (eg, atazanavir, indinavir, ritonavir, or saquinavir)
  • iron supplements, such as ferrous fumarate, ferrous gluconate, or ferrous sulfate
  • loperamide
  • metformin
  • multivitamins
  • theophylline
  • warfarin.

Note that this list is not all-inclusive and includes only common medications that may interact with Zantac. You should refer to the prescribing information for Zantac for a complete list of interactions.  


Further information

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.

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

Copyright 1996-2021 Revision date: November 4, 2021.