FDA on Wednesday announced that it has found "unacceptable levels" of the cancer-causing chemical it has detected in ranitidine drugs used to treat heartburn, including the common brand-name drug Zantac.

Background: FDA finds cancer-causing chemical in another US drug

FDA last month announced that it had found low levels of a chemical that could cause cancer in some batches of medications commonly used to treat heartburn. The chemical, called N-nitrosodimethylamine (NDMA), is the same carcinogen FDA has detected in the common heart drug valsartan. According to FDA, NDMA is an environmental contaminant typically found in foods—including dairy products, meats, and vegetables—and water. NDMA is an impurity the International Agency for Research on Cancer has classified as a probable human carcinogen, meaning it is a substance that could cause cancer.

FDA said since last year it has been investigating NDMA and other impurities found in heart failure treatments, and has issued recalls for those medications because they contained "unacceptable levels of nitrosamines."

However, FDA last month said it had detected only low levels of NDMA in some batches of ranitidine medications, including the brand-name heartburn treatment Zantac and generic versions of the drug. The medications are available by prescription and over the counter (OTC).

FDA at the time said it was still evaluating whether the levels of NDMA it has detected in ranitidine drugs posed health risks to individuals who have taken the medications, but said preliminary testing had shown the levels of NDMA found in the heartburn drugs "barely exceed[ed] amounts you might expect to find in common foods."

As such, FDA did not issue recalls of Zantac or other ranitidine drugs.

FDA finds 'unacceptable' levels of NDMA in heartburn drugs

But FDA on Wednesday said early, limited testing has now detected "unacceptable levels" of NDMA in some samples of ranitidine drugs.

The agency said it is continuing to test ranitidine drug samples from various manufacturers and is examining the potential effects that the chemical might have on patients who have taken the drugs. Further, FDA said it has asked manufacturers to conduct their own tests on ranitidine drugs to assess whether they contain NDMA, and to send samples of the drugs to FDA for testing by scientists at the agency.

FDA said it will provide additional information on the matter "as it becomes available."

Major retailers suspend sales of ranitidine drugs

The news has sparked some major retailers—including CVS Health, Rite Aid, Walgreens Boots Alliance, and Walmart—to suspend OTC sales of Zantac and other ranitidine drugs.

In addition, drugmaker Novartis last month stopped distribution of its ranitidine drugs across the globe.

Drugmaker Sanofi has said it is not halting shipments of ranitidine drugs in the United States.

FDA has said there are other heartburn medications available that do not contain ranitidine if patients want to stop taking ranitidine drugs, though the agency has not issued a recall of the medications and is not recommending that patient stop using the drugs. FDA said patients that want to stop using ranitidine drugs should consult their health care providers (Joseph, Reuters, 10/2; FDA release, 10/2; AP/Modern Healthcare, 10/2; Molina, USA Today, 10/1).