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Ranitidine: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Nov 3, 2021.

1. How it works

  • Ranitidine 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, ranitidine prevents histamine from having this effect, thereby reducing gastric acid secretion.
  • Ranitidine is specific for H2 receptors (other drugs, called antihistamines, block H1 receptors which are primarily involved with allergic-type reactions).
  • Ranitidine belongs to a group of drugs known as H2 receptor antagonists (also called H2 blockers).
  • Ranitidine was withdrawn from the U.S. market in 2020.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 secretion 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.
  • Ranitidine may be sold over-the-counter in approved packaging which means adults and children older than 12 years may self-medicate with ranitidine for mild gastrointestinal complaints such as occasional heartburn, indigestion, or sour stomach brought on by certain foods.
  • May be used in addition to antacids.
  • Generic ranitidine is available.

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) are the most commonly reported side effects. Other side effects are rare.
  • May cause false-positive results on urine protein tests and higher dosages may affect liver function.
  • A response to ranitidine does not mean that your symptoms are not due to gastric or duodenal cancer (stomach cancer affects over 26,000 people in the U.S. each year; the risk is higher in older people). Endoscopy is the only way to check for stomach cancer.
  • The dosage of ranitidine should be adjusted in people with kidney disease, and a dosage reduction should be considered in those with liver disease.
  • Avoid in people with acute porphyria (a group of disorders characterized by the build-up of porphyrin-producing natural chemicals).
  • May interact with some other medications including warfarin, HIV antivirals, nifedipine, procainamide, and benzodiazepines.
  • Vitamin B12 deficiency may occur with long-term therapy.
  • In early 2020, the FDA requested the removal of all ranitidine products 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).
  • Only use during pregnancy if benefits clearly outweigh the harms. Animal studies have failed to reveal evidence of impaired fertility or fetal harm but their are few human studies. It is unknown if there is a link between the use of gastric-suppressing drugs during pregnancy and childhood allergy and asthma. Ranitidine is excreted into human milk but there is no data on adverse effects. It is also known to increase prolactin levels. There is no data on galactorrhea. Caution is recommended.

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

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

5. Tips

  • May be taken with or without food. Take with a glass of water and take the exact dosage as directed on the packet (self-medicating) or by your doctor (prescribed).
  • 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 taken alongside ranitidine if needed for gastric-acid associated pain.
  • Effervescent forms of ranitidine for adults should be dissolved in a 6-8 ounce glass of water prior to ingestion. 25mg effervescent tablets for children should be dissolved in more than 5mL of water and the resultant solution administered to the child with a dropper or oral syringe. Effervescent tablets should not be chewed, swallowed whole, or dissolved on the tongue.
  • Do not self-medicate with ranitidine if you are over the age of 40 and this is the first time you have had heartburn or indigestion; have a family history of gastric cancer; have coughing spells; use NSAIDs anti-inflammatories (such as aspirin or ibuprofen); have difficulty or pain when swallowing; already take other drugs (other than antacids) for indigestion or heartburn; are pregnant or breastfeeding; have acute porphyria (do not use ranitidine at all); or have blood in your vomit or stools. Instead, make an appointment with your doctor.
  • Phenylketonurics should avoid Zantac EFFERdose which contains aspartame which is metabolized to phenylalanine.
  • Smoking can affect how well ranitidine works and how quickly duodenal ulcers heal.
  • Some symptoms of stomach cancer may be similar to heartburn. Seek medical advice if your symptoms are persistent or severe.

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 ranitidine therapy.
  • One 150mg dose of ranitidine substantially inhibits gastric acid secretion for approximately 9.5 hours.
  • Food does not appear to affect the absorption of ranitidine or its peak concentration.

7. Interactions

Medicines that interact with ranitidine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with ranitidine. 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 ranitidine 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 ranitidine. You should refer to the prescribing information for ranitidine 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 ranitidine only for the indication prescribed.

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

Copyright 1996-2022 Revision date: November 2, 2021.