Zantac is a heartburn drug available by prescription and over the counter. It has been on the market since 1981.

Sandoz, a division of Novartis AG, announced on September 18 that it would stop worldwide distribution of all ranitidine-containing medicines, including brand-name and generic Zantac, because of potential impurities in the heartburn medication.

This new decision came a few days after the U.S. Food and Drug Administration (FDA) released a statement alerting healthcare professionals and consumers that low levels of the probable human carcinogen N-nitrosodimethylamine (NDMA) was found in some ranitidine medicines, including Zantac.

“The FDA is continuing to investigate how long NDMA has been present in ranitidine and will communicate information on the risk to patients as it becomes available,” an FDA spokesperson, Jeremy Kahn, told Everyday Health.

Another distributor of ranitidine, Dr. Reddy’s Laboratories Ltd., announced on September 20 that they were also suspending distribution as a precautionary measure.

Considered Safe for Decades, Zantac May Carry Risks

Zantac, also known as ranitidine, belongs to a group of drugs called histamine-2 or H-2 blockers, which decrease stomach acid and are used to treat acid reflux. The drug was first available on the market in 1981 and was the second drug in history to reach a billion dollars in sales. In 1988 Zantac was the single largest-selling prescription drug ever, according to a New York Times report.

This current contamination issue is in the manufacturing and not a problem with the active molecule ranitidine, says Emeran A. Mayer, MD, a gastroenterologist and the codirector of the CURE Digestive Diseases Research Center at UCLA Health in Los Angeles. “If it had been a problem with the molecule, we would have seen the negative effects a long time ago,” says Dr. Mayer.

It’s unclear right now how NDMA got into the production pipeline or how long it’s been present, he says. The FDA is currently working with international regulators and industry partners to find that out, according to a statement from Janet Woodcock, MD, the director of the Center for Drug Evaluation and Research.

NDMA: What It Is and What the Risks Are

There’s no question that NDMA is carcinogenic (meaning that it is known to cause cancer). It’s one of the compounds in cured meats, says Mayer, and “there’s an increased cancer risk if you eat a lot of cured meats.” The World Health Organization (WHO) classified processed meat as a carcinogen in 2015.

In addition to cured meats like bacon, there are several ways people can be exposed to NDMA in everyday life, according to the Centers for Disease Control and Prevention (CDC), including tobacco smoke, chewing tobacco, beer, fish, and cheese, as well as through household items like shampoo and detergent.

This would not be the first time NDMA has been identified in a pharmaceutical product. Last year the chemical was found in valsartan, a blood pressure medication sold under the brand name Diovan. Because the FDA deemed the amount of NDMA unacceptable, several lots of the drug were recalled.

Although NDMA may cause harm in large amounts, the levels that the FDA has found so far in ranitidine from preliminary tests, “barely exceed amounts you might expect to find in common foods,” according to the FDA statement.

Should I Stop Taking Zantac?

The FDA is not calling for individuals to stop taking ranitidine at this time. According to the statement, people taking prescription ranitidine who want to stop using it should talk to their healthcare professional about other treatment options. People taking OTC ranitidine could consider using other OTC products approved for their condition, said the FDA. Mayer says consumers should be “moderately concerned” about the risk of using these drugs.

Your decision should be partly based on how long you need to take Zantac, says Mayer. “If you are taking the drug on a short-term basis, there’s no reason for concern. This is not something that’s acutely dangerous. If you take this medication for a week or even a month and then stop it, I don’t think there would be any enhanced risk,” he says.

“On the other hand, if you are on this drug on a long-term basis, I think until it’s all clarified and the whole story comes out, I would recommend talking with your physician about substituting it with another H2 blocker or with a proton pump inhibitor like omeprazole or Prilosec,” says Mayer. There are several medications that you could replace Zantac with, he adds. “Until all this is resolved, and we have an explanation for why NDMA is present, it’s possible there could be some associated risks with long-term use,” says Mayer.