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Zantac (ranitidine) is an anti-acid drug available over the counter and by prescription. It belongs to a class of drugs called H2 (histamine-2) blockers. In its OTC form, Zantac is used to treat heartburn and acid indigestion. In prescription strength, it’s used to treat ulcers, GERD and erosive esophagitis.

Last Modified: May 5, 2021
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The antacid Zantac — known as ranitidine in generic form — was available over the counter or as a prescription in the Unites States until April 2020. After the market withdrawal of ranitidine products, Sanofi reformulated an over-the-counter version of Zantac 360 made with famotidine. This page presents information about Zantac made with ranitidine.

People could take ranitidine orally in pill and liquid form or intravenously as an injection. GlaxoSmithKline first received FDA approval for Zantac in 1983, and by 1988 it was the world’s best-selling drug, bringing in $1 billion in annual sales.

Sanofi was the last company to market brand-name Zantac with ranitidine in the United States. In 2018, Sanofi reported it made 113 million euros, the equivalent of roughly $124 million in the United States.

According to Bloomberg Intelligence, nearly 25 million prescriptions for ranitidine were written in 2018.

Zantac side effects are typically mild and pass quickly. The most commonly reported adverse events include constipation, diarrhea and nausea or vomiting. Rarely, some serious side effects such as skin rashes, liver failure and cardiac disorders may occur.

In April 2020, the U.S. Food and Drug Administration requested manufacturers of Zantac and its generic forms withdraw all prescription and over-the-counter versions of the drugs immediately over concerns of contamination with N-Nitrosodimethylamine, or NDMA, a chemical impurity that could cause cancer.
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How Does Ranitidine Work?

Ranitidine, the active ingredient in Zantac, belongs to a class of antacid drugs called H2 blockers, or histamine-2 receptor agonists.

H2 receptor agonists work by blocking histamine from parietal cells that line the stomach. This prevents the stimulation of the proton pump, an enzyme that transports hydrochloric acid secreted by the parietal cell. Inhibiting the proton pump reduces the amount of acid in the stomach, which, in turn, reduces symptoms of gastric disorders such as heartburn, GERD and gastric ulcers.

Zantac starts to work in as little as 30 minutes. It can control acid production for up to 12 hours and reduce the frequency and severity of heartburn.

Over-the-counter and prescription Zantac have different instructions for use. Depending on the reason for the health provider prescribing Zantac, the dosages will vary.

Hospitals use the Zantac injection for patients with pathological hypersecretory conditions or intractable duodenal ulcers, or as an alternative to the oral medication.

OTC Directions

OTC Zantac treats heartburn with acid indigestion and sour stomach caused by eating or drinking certain foods or beverages. Children under 12 should not use Zantac without first getting approval from a health care provider.

Directions for adults and children 12 years and over:

  • Swallow one tablet with a glass of water for symptom relief.
  • To prevent heartburn, swallow one tablet with a glass of water 30 to 60 minutes before eating or drinking.
  • Do not take more than two tablets in 24 hours.
  • Do not chew tablet.

Prescription Directions and Recommended Dosages

Prescription Zantac treats several acid-related conditions, from GERD to erosive esophagitis.

Children as young as one month old may take the drug, but researchers have not studied it in children younger than one month and cannot make dosing recommendations.

Providers should adjust the dosage for people with impaired kidney function.

Dosing Instructions
Active Duodenal Ulcer150 mg twice daily or 300 mg once daily after the evening meal or at bedtime
Maintenance of Healing of Duodenal Ulcers150 mg at bedtime
Pathological Hypersecretory Conditions (such as Zollinger-Ellison syndrome)150 mg twice a day. Some patients may need to administer ranitidine 150 mg doses more frequently. Providers may increase the dosage up to 6 g a day.
Benign Gastric Ulcer150 mg twice a day
Maintenance of Healing of Gastric Ulcers150 mg at bedtime
GERD150 mg twice a day
Erosive Esophagitis150 mg four times a day
Maintenance of Healing of Erosive Esophagitis150 mg twice a day
Pediatric Treatment of Duodenal and Gastric Ulcers2 to 4 mg/kg twice daily to a maximum of 300 mg/day
Pediatric Maintenance of Healing of Duodenal and Gastric Ulcers2 to 4 mg/kg once daily to a maximum of 150 mg/day
Pediatric Treatment of GERD and Erosive Esophagitis 5 to 10 mg/kg per day, usually given as two or three divided doses

Zantac Drug Interactions

Tell your health care provider about all medications, herbal supplements and vitamins you take before taking Zantac. Avoid drinking alcohol with the drug because it may increase the risk of stomach damage.

Because ranitidine affects stomach acid, it may increase or decrease the effectiveness of drugs that rely on stomach acid to be effective.

There are no interactions listed for Zantac OTC, but the prescription drug label includes several.

Drugs That May Interact with Zantac
Drug absorption may be impaired, use with caution.
Drug absorption may be impaired, use with caution.
Gefitinib exposure was reduced when used with ranitidine, use with caution.
Glipizide exposure increased after a single 150-mg dose of oral ranitidine in diabetic patients.
Oral ketoconazole exposure was reduced by up to 95% when used with ranitidine.
Oral midazolam increased when used with ranitidine and may cause excessive and prolonged sedation.
Higher doses of ranitidine (>300 milligrams/day) may increase levels plasma levels of this drug and in rare cases may cause toxicity.
Oral Triazolam increased when used with ranitidine and may cause excessive or prolonged sedation.
Ranitidine may affect warfarin’s effectiveness.

Zantac vs. Prilosec

Zantac works differently from Prilosec, which belongs in the proton pump inhibitor class. Deciding which type of drug to use depends on how bad the symptoms are and how often they occur.

Antacids, H2 blockers and PPIs as heartburn medications
Zantac can control acid longer than Tums but not as long as Prilosec.
Differences Between Zantac and Prilosec
DrugHow It WorksHow Long it Takes to WorkHow Long It Lasts
Zantac (H2 Blockers)Reduces stomach acid production, can provide immediate relief30 minutes to an hourUp to 12 hours
Prilosec (Proton Pump Inhibitor PPI)Blocks acid production, treats frequent heartburn and not intended for immediate relief May take 1 to 4 days to workUp to 24 hours when used daily

Recalls and Lawsuits over Contaminated Ranitidine

Starting on Sept. 24, 2019, some manufacturers began voluntary Zantac recalls of certain lots of the drug because of contamination with N-nitrosodimethylamine, or NDMA — a chemical that may cause cancer.

The FDA had previously announced recalls of valsartan and blood pressure drugs losartan and irbesartan that had been contaminated with NDMA.

At first, the agency didn’t agree that NDMA levels present in ranitidine were too high. But after preliminary testing of some drug samples, on Oct. 2, 2019, the FDA stated that contamination levels were “unacceptable.”

On Nov. 1, 2019, the agency announced that it had found NDMA in all the drug samples it tested. It determined that “the levels of NDMA in ranitidine and nizatidine are similar to the levels you would expect to be exposed to if you ate common foods like grilled or smoked meats.”

The FDA set the daily acceptable limit for NDMA consumption at 96 nanograms — 0.32 parts per million, or ppm. It recommended that all manufacturers with levels above this limit recall their products.

FDA Updates
The FDA recommends checking its ranitidine updates and press announcements page for details on specific lot numbers and company recalls.

Walmart, CVS, Walgreens and Rite Aid pulled all brand-name and generic Zantac from store shelves.

Then, on April 1, 2020, the FDA announced that its studies had revealed that NDMA in some ranitidine products increases over time and when stored at higher than room temperatures. As a result, the agency said, consumers could be exposed to unacceptable levels of NDMA.

The FDA requested an immediate market withdrawal of all ranitidine products. According to the agency, consumers taking OTC ranitidine should stop taking the drug, dispose of their supply properly and not buy more. Patients taking prescription ranitidine should speak with their doctor or other health care provider about alternatives. This recall and withdrawal doesn’t affect the new Zantac 360 over-the-counter formula made with famotidine.

Lawsuit Information
Lawsuits claim high levels of the cancer-causing chemical N-Nitrosodimethylamine, or NDMA, in Zantac can increase the risk of bladder, stomach and other cancers.
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People with Cancer File Lawsuits

Shortly after the first recalls, people began filing Zantac lawsuits and claimed the drug was responsible for causing cancer. Companies named in lawsuits include Zantac manufacturers Sanofi and Pfizer.

On Feb. 6, 2020, the United States Judicial Panel on Multidistrict Litigation consolidated 140 cases in MDL No. 2924 in the Southern District of Florida under U.S. District Judge Robin Rosenberg. Plaintiffs’ attorneys have predicted a large number of cases.

The lawsuits allege that manufacturers knew that ranitidine could form NDMA in the human body and increase cancer risk, but failed to inform consumers.

Zantac Alternatives

Because of concerns that NDMA in Zantac can increase cancer risk, the FDA told all manufacturers to remove all Zantac and other ranitidine products from the U.S. market in April 2020. People who depended on the drug to control acid reflux and other acid-related disorders have a few Zantac alternatives.

Medication alternatives include proton pump inhibitors and other H2 blockers. People who want to switch medication should speak to their medical provider before stopping any drug.

Proton Pump Inhibitors

Proton pump inhibitors are powerful acid-reducing drugs that can control acid for up to 24 hours if taken every day.

The FDA recommends the following PPIs as Zantac alternatives:

H2 Blockers

The FDA has tested other H2 blockers and did not find NDMA contamination. FDA-recommended H2 blockers include Pepcid (famotidine) and Tagamet (cimetidine). In addition, Sanofi has released a new over-the-counter Zantac 360 formula made with famotidine, the same active ingredient in Pepcid.

These drugs work similarly to Zantac with ranitidine, but each has slightly different side effects. Pepcid has fewer common side effects than Tagamet and is more tolerable.

Pepcid’s most common side effect is headache, while Tagamet has a longer list. These include rashes, diarrhea, dizziness, headache and gynecomastia — a disorder that causes men to grow breasts.

Please seek the advice of a medical professional before making health care decisions.