Forty-three more lots of a blood pressure medication have been recalled because of concerns they may contain trace amounts of a potentially cancer-causing impurity. It's the latest in a series of recalls since last July, which has seen a spike in recent weeks.

Legacy Pharmaceutical Packaging, LLC, announced Friday it was recalling the lots of Losartan Tablets USP because they may contain N-Nitroso N-Methyl 4-aminobutyric acid (NMBA), a potential human carcinogen. Legacy said there was a possible process impurity or contaminant in an active pharmaceutical ingredient (API), manufactured by another company, Hetero Labs Limited.

The nationwide recall involves 40 repackaged lots of Losartan Tablets USP 25mg, 50mg, and 100mg, and three prepackaged lots of Losartan Tablets USP 50mg. Losartan is a prescription medication used to treat high blood pressure and congestive heart failure.

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Legacy said it has not received any reports of adverse reactions to using the medication.

This now makes at least six blood pressure medication recalls due to potential cancer risk since February 22. The FDA said the impurities might be happening when specific chemicals and reaction conditions are present in the manufacturing process of the drug’s API (active pharmaceutical ingredients). It may also result from the reuse of materials, such as solvents.