The list of companies recalling drugs that contain an ingredient with a potentially deadly impurity has expanded. The ingredient is valsartan and is used to treat high blood pressure and heart failure, according to the FDA. An impurity called N-nitrosodimethylamine (NDMA) was found in the drug.

NDMA is classified as a probable human carcinogen based on lab tests.

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The recall was first announced in July and promoted a wave of concern from heart patients who said they've used the drug for years and have been diagnosed with different cancers.

The FDA said this sudden presence of NDMA is because of the way the substance was manufactured.

The expanded list of companies recalling drugs with the ingredient can be found here.

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Patients who are taking one of the recalled medicines listed above should follow the recall instructions that are provided by the FDA's website.

An important note to add for patients who are taking valsartan is that this medication is used to treat various other serious medical conditions and if a patient is taking the recalled medication, they should continue to take it until a replacement product is made available, according to the FDA.

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Also, patients are encouraged to contact their doctor or the pharmacy that dispensed the impacted drugs to discuss an alternative option.

“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. This is why we’ve asked these companies to take immediate action to protect patients,” said Janet Woodcock, M.D., director of the FDA’s Center for Drug Evaluation and Research.

The FDA is continuing to investigate the issue and will add more information as it becomes available.