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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. Zantac reduces the secretion of gastric acid in the stomach by blocking the effect of histamine on histamine H2 receptors located on the parietal cells lining the stomach wall. Histamine is the chemical transmitter that stimulates the parietal cells to release gastric acid. By blocking H2 receptors, Zantac prevents histamine from having this effect, thereby reducing gastric acid secretion.
  • Zantac is specific for H2 receptors (other drugs, called antihistamines, block H1 receptors which are primarily involved with allergic-type reactions).
  • Zantac belongs to a group of drugs known as H2 receptor antagonists (also called H2 blockers).
  • Zantac was withdrawn from the U.S. market in 2020. This was because a contaminant known as N-Nitrosodimethylamine (NDMA) was found in ranitidine-containing medications. This contaminant increased in concentration over time and when Zantac was stored at higher than room temperature. NDMA is a probable human carcinogen (a substance that could cause cancer).
  • This patient tip is retained for education purposes only.

2. Upsides

  • Zantac was used for the short-term treatment of active duodenal or gastric ulcers.
  • Reduced stomach acid secretion so was used for the treatment of gastroesophageal reflux disease (GERD) or hypersecretory conditions such as Zollinger-Ellison syndrome, systemic mastocytosis, and endoscopically diagnosed erosive esophagitis.
  • Zantac was sold over-the-counter in approved packaging which allowed adults and children older than 12 years to self-medicate for mild gastrointestinal complaints such as occasional heartburn, indigestion, or sour stomach brought on by certain foods.
  • Was used in addition to antacids.
  • Zantac was available as a generic under the name ranitidine.

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, and abdominal pain) were the most commonly reported side effects. Other side effects were rare.
  • May have caused false-positive results on urine protein tests and higher dosages could affect liver function.
  • The dosage of Zantac needed to be adjusted in people with kidney disease and considered for those with liver disease.
  • Not for people with acute porphyria (a group of disorders characterized by the build-up of porphyrin-producing natural chemicals).
  • There was a potential for interaction with some other medications including warfarin, HIV antivirals, nifedipine, procainamide, and benzodiazepines.
  • Vitamin B12 deficiency could occur with long-term therapy.
  • In early 2020, the FDA requested the removal of all ranitidine-containing products, including Zantac, from the market. This was because a contaminant known as N-Nitrosodimethylamine (NDMA) was found in ranitidine-containing medications. This contaminant increased in concentration over time and when ranitidine was stored at higher than room temperature. NDMA is a probable human carcinogen (a substance that could cause cancer).
  • Only used during pregnancy if the benefits outweighed the harms. Animal studies failed to reveal evidence of impaired fertility or fetal harm but there were few human studies. It was unknown if there is a link between the use of gastric-suppressing drugs during pregnancy and childhood allergy and asthma. Ranitidine was excreted into human milk but there is no data on adverse effects. It also increased prolactin levels.

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 was an acid-suppressing agent that was used to treat a wide range of gastric-acid-related disorders, including gastric ulcers, heartburn, and GERD. Headaches were the most common side effect. Products containing ranitidine, including Zantac, were withdrawn from the U.S. market in 2020.

5. Tips

  • Do not take Zantac because of the risk of NDMA contaminants.

6. Response and effectiveness

  • Peak effects are reached two to three hours after taking a 150mg dose. Symptomatic relief of GERD occurs within 24 hours of starting Zantac.
  • One 150mg dose of Zantac substantially inhibits gastric acid secretion for approximately 9.5 hours.
  • Food does not appear to affect the absorption of Zantac or its peak concentration.

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.

Zantac is no longer available in the United States.  


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 1996-2023 Revision date: December 30, 2022.