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Zantac is an anti-acid drug available over the counter and with a prescription. In its OTC form, it treats heartburn and acid indigestion. In prescription strength, it treats ulcers, GERD and erosive esophagitis. It starts to work in as little as 30 minutes and can last up to 12 hours. Potential drug interactions include warfarin, ketoconazole and atazanavir.

The antacid Zantac — known as ranitidine in generic form — is available over the counter or as a prescription. People can take the drug 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.

Currently, Sanofi markets brand-name Zantac in the United States. In 2018, the company 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.
Source: U.S. Food and Drug Administration
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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.

How to Take the Drug

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
Indication Dose/Instructions
Active Duodenal Ulcer 150 mg twice daily or 300 mg once daily after the evening meal or at bedtime
Maintenance of Healing of Duodenal Ulcers 150 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 Ulcer 150 mg twice a day
Maintenance of Healing of Gastric Ulcers 150 mg at bedtime
GERD 150 mg twice a day
Erosive Esophagitis 150 mg four times a day
Maintenance of Healing of Erosive Esophagitis 150 mg twice a day
Pediatric Treatment of Duodenal and Gastric Ulcers 2 to 4 mg/kg twice daily to a maximum of 300 mg/day
Pediatric Maintenance of Healing of Duodenal and Gastric Ulcers 2 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
Drug How It Works How Long it Takes to Work How Long It Lasts
Zantac (H2 Blockers) Reduces stomach acid production, can provide immediate relief 30 minutes to an hour Up 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 work Up 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.

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.
View Lawsuits

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).

These drugs work similarly to Zantac, 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.

Zantac Facts
  1. Manufacturer Sanofi/Chattem in the United States, GlaxoSmithKline in the U.K. and the world, Boehringer Ingelheim and various generics
  2. Used to Treat Heartburn, indigestion, GERD, Zollinger-Ellison syndrome, ulcers, erosive esophagitis
  3. Related Drugs Prilosec, Nexium, Prevacid, Pepcid, Tagamet
  4. Active Ingredient Ranitidine
  5. Administration Route Oral, injection
  6. Available Strength 25, 75, 150, 300 mg
  7. Dosage Form Tablet, injection
  8. Drug Class H2 Blockers
  9. Is Available Generically True
  10. Is Proprietary True
  11. RxCUI 152523

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

Michelle Llamas, Senior Content Writer
Written By Michelle Llamas Senior Writer

Michelle Llamas has been writing articles and producing podcasts about drugs, medical devices and the FDA for nearly a decade. She focuses on various medical conditions, health policy, COVID-19, LGBTQ health, mental health and women’s health issues. Michelle collaborates with experts, including board-certified doctors, patients and advocates, to provide trusted health information to the public. Some of her qualifications include:

  • Member of American Medical Writers Association (AMWA) and former Engage Committee and Membership Committee member
  • Centers for Disease Control and Prevention (CDC) Health Literacy certificates
  • Original works published or cited in The Lancet, British Journal of Clinical Pharmacology and the Journal for Palliative Medicine
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24 Cited Research Articles writers follow rigorous sourcing guidelines and cite only trustworthy sources of information, including peer-reviewed journals, court records, academic organizations, highly regarded nonprofit organizations, government reports and interviews with qualified experts. Review our editorial policy to learn more about our process for producing accurate, current and balanced content.

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