Some drugs used to control high blood pressure and prevent heart failure were voluntarily recalled this past week due to an impurity that could possibly lead to cancer, the U.S. Food and Drug Administration said.

These products — with the active ingredient valsartan, a generic drug used to treat high blood pressure — may contain N-nitrosodimethylamine (NDMA), a possible human carcinogen. The FDA asked three companies, Major Pharmaceuticals, Solco Healthcare and Teva Pharmaceuticals Industries Ltd., to recall their valsartan products. Solco and Teva were also asked to recall their drugs containing valsartan/hydrochlorothiazide (HCTZ).

“We have carefully assessed the valsartan-containing medications sold in the United States, and we’ve found that the valsartan sold by these specific companies does not meet our safety standards,” said Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, in a statement. “This is why we’ve asked these companies to take immediate action to protect patients.”

The FDA is now looking into the potential impacts the drugs have had on patients who have already taken them, as well as how to get rid of the impurity from future batches of these products. The agency advised patients taking the products to continue to do so until they have a suitable replacement.

Companies impacted by the recall have shared instructions for patients impacted by these products. The FDA also said patients should talk to their pharmacists and doctors who prescribed the medicine to discuss their next steps.

Earlier this year, the European Medicines Agency announced it was reviewing medicine with an active valsartan ingredient supplied by Zhejiang Huahai Pharmaceuticals, a China-based company, for the same reason. Zhejiang Huahai Pharmaceuticals supplied the three U.S.-based pharmaceutical companies with these products, according to The New York Times.

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