For the fourth time in the past year, a widely used blood pressure medication is under review amid concerns it could contain chemicals that could potentially cause cancer.

Valisure, an online pharmacy licensed in 37 states, has alerted the Food and Drug Administration of high levels of dimethylformamide (DMF) in valsartan, which is produced by several pharmaceutical companies and often combined with other medicines into a single pill.

DMF is classified as a probable human carcinogen by the World Health Organization and the American Cancer Society.

The pharmacy is asking a recall for the pills and requesting the FDA revise its acceptable intake levels of DMF from the current level of 8,800,000 nanograms to under 1,000 nanograms. The FDA has not yet responded to that request. The government agency is evaluating the findings.

Patients are being advised to continue taking the medicine for now, since abruptly discontinuing the pills can have negative effects.

Valisure says it found excessive DMF levels in valsartan products from six companies.

Blood pressure medications have been put under increasing scrutiny of late, with several recalls in the past year. In February, the FDA expanded its recall on Losartan. Irbesartan doses were recalled last November. And companies including Major Pharmaceuticals, Solco Healthcare, and Teva Pharmaceuticals have recalled numerous lots of medications that contain valsartan, and Teva has now recalled all non-expired valsartan-containing products it sells on the U.S. market, including amlodipine-valsartan and amlodipine-valsartan-hydrochlorothiazide combination tablets.

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