TORONTO -- The U.S. Food and Drug Administration announced Wednesday that it is asking manufacturers and pharmacies to cease production and sale of over-the-counter Zantac, a medication that treats heartburn, due to potential contamination.

According to the FDA, the medication could contain a nitrosamine impurity called N-nitrosodimethylamine (NDMA).

An investigation into the levels of NDMA within ranitidine medication has been ongoing since the summer of 2019, when laboratory testing found NDMA in ranitidine. Ranitidine is a drug that blocks the over-production of acid, and can be used to treat and prevent ulcers in the stomach as well as heartburn.

Zantac is the brand name for ranitidine medication. The recall extends to generic versions of ranitidine as well.

The FDA said last September that “NDMA is classified as a probable human carcinogen (a substance that could cause cancer) based on results from laboratory tests.”

NDMA is present in low levels in both food and water, the FDA said in their newest press release.

“These low levels would not be expected to lead to an increase in the risk of cancer,” the release states. “However, sustained higher levels of exposure may increase the risk of cancer in humans.”

After months of investigation, the FDA found that the levels of NDMA in ranitidine medications increase “even under normal storage conditions,” and increase at a higher rate when exposed to temperature increases — including increases that might occur during distribution and handling by customers.

“We didn’t observe unacceptable levels of NDMA in many of the samples that we tested. However, since we don’t know how or for how long the product might have been stored, we decided that it should not be available to consumers and patients unless its quality can be assured,” said Janet Woodcock, M.D., director of the FDA’s Center for Drug Evaluation and Research, in the FDA’s press release.

In September of 2019, Health Canada asked for companies to stop any further distribution of ranitidine medication as a “precautionary measure.” This was described as an “interim measure,” in a statement, and they specified that it was different than a recall, as pharmacies could continue distributing their existing stock.

Several companies voluntarily recalled their ranitidine drugs in Canada over the fall as a response.

Health Canada has not issued a mass recall of the medication in Canada following the FDA’s announcement.  

They told in an emailed statement that they are working “with companies and international partners to understand the root causes of nitrosamines in drugs.

“The Department will take action if a risk to Canadians is identified, and will be vigilant in informing the public of any new safety information,” they said.

The FDA have recommended that anyone who currently takes the medication stops using it, and finds over approved over-the-counter products to replace Zantac with.