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More common heartburn medications have been recalled due to the presence of an impurity that might cause cancer.

Denton Pharma Inc. this week recalled several batches of ranitidine tablets. The recall impacts all unexpired lots of 150 mg and 300 mg tablets. The pills were distributed to Northwind Pharmaceuticals LLC and Crosswind Pharmacy.

Appco Pharma LLC also recalled 150 mg and 300 mg batches of its ranitidine hydrochloride capsules.

So far there have not been any reports of people getting sick related to these recalls, but the medications may be contaminated with N-Nitrosodimethylamine, also known as NDMA.

NDMA is an impurity that is considered a possible carcinogen by the US Environmental Protection Agency. NDMA can be unintentionally introduced into manufacturing through certain chemical reactions.

The US Food and Drug Administration has been testing several drugs after it found the impurity in blood pressure and heart failure medicines known as ARBs. The investigation has been going on since 2018.

In October, several major retailers announced they would halt sales of ranitidine medications because of concerns they might contain the impurity. Last year, drug maker Novartis said it would stop distribution of all ranitidine medicines made by Sandoz; Dr. Reddy’s Laboratories Ltd. recalled its ranitidine medicines; and Sanofi recalled Zantac OTC, its popular heartburn medication.

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The FDA has been trying to determine what is causing this problem and has been working with international regulators to determine how the impurities are getting into these drugs.