(CNN) -- As part of its investigation into an impurity found in heartburn medication Zantac OTC, the US Food and Drug Administration has found levels of the impurity "similar to the levels you would expect to be exposed to if you ate common foods like grilled or smoked meats."
Laboratory test results showed that, within the human digestive system, the Zantac medication does not form the impurity known as N-nitrosodimethylamine or NDMA, said Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, in a statement on Friday.
Zantac is a type of ranitidine, a medication for heartburn, stomach ulcers and other conditions that cause too much stomach acid.
"The information we've gathered as part of our ongoing ranitidine investigation has been vital to answering the questions we've received about the potential risk of these products," Woodcock said.
"We also conducted tests that simulate what happens to ranitidine after it has been exposed to acid in the stomach with a normal diet and results of these tests indicate that NDMA is not formed through this process," she said. "Similarly, if ranitidine is exposed to a simulated small intestine environment, NDMA is not formed. However, we still must test the drugs in the human body to fully understand if ranitidine forms NDMA."
NDMA has been classified as a probable human carcinogen based on lab tests, and concern around Zantac containing levels of the impurity emerged in September.
The FDA released a statement in September stating that it had learned that some ranitidine medicines, including Zantac, contain low levels of NDMA.
In the weeks following that statement, retailers Walmart, CVS Pharmacy and Walgreens pulled Zantac and other over-the-counter ranitidine medications from their shelves and the drugmaker Sanofi voluntarily recalled the medication.
Now it turns out that "although many of these levels of NDMA observed through FDA testing are much lower than the levels some third-party scientists first claimed, some levels still exceed what the FDA considers acceptable for these medicines," Woodcock said.
The "acceptable limits" of NDMA are 96 nanograms per day or 0.32 ppm. In Woodcock's statement, she said that if the FDA or manufacturers find NDMA levels above that limit, companies will be asked to voluntarily recall their ranitidine products.
"We would also ask manufacturers to voluntarily recall nizatidine, commonly known as Axid, if they found NDMA above the acceptable daily intake level because it is chemically similar to ranitidine," Woodcock said, adding that manufacturers should continue conducting their own lab tests.
"We are still working with manufacturers to investigate the true source of NDMA and to understand the root cause of the low levels of NDMA present in the drugs," she said.
If you take over-the-counter ranitidine products or nizatidine, antacid medications, the FDA recommends considering other over-the-counter products for their conditions.
FDA tests of other medications, like Pepcid, Tagamet, Nexium, Prevacid and Prilosec, have shown no NDMA impurities in the medicines, according to Woodcock's statement. If you take prescription ranitidine or nizatidine, you should talk to your doctor about other treatment option.
"There are multiple drugs approved for the same or similar uses as ranitidine and nizatidine," Woodcock said.
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