Just when it appeared the FDA was close to purging the U.S. drug supply of potential cancer-causing impurities in sartan blood pressure drugs, another massive recall has been launched. This time it is for an entirely new contaminant.

The FDA on Friday announced that India’s Hetero Labs was recalling 87 lots of losartan potassium tablets distributed by Camber Pharmaceuticals because they contain the impurity, N-Nitroso-N-methyl-4-aminobutyric acid (NMBA). The drugs were manufactured from an API produced by Aurobindo Pharma, USA.

On Tuesday, the FDA announced that Torrent Pharmaceuticals recalled 60 lots of Losartan potassium tablets USP and 54 lots of Losartan potassium/ hydrochlorothiazide tablets, because they were made with an API from Hetero Labs which contained NMBA.

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Like previous impurities, the NMBA is believed to have been created in the manufacturing process and may result from the reuse of materials, such as solvents, the FDA said.

FDA Commissioner Scott Gottlieb in a statement, said the new impurity had not been found in the previously recalled products that contained NDEA and NDMA. Like those impurities, he said the overall risk of contracting cancer from taking drugs that contain NMBA is very low.

“We are deeply concerned about the presence of a third nitrosamine impurity in certain ARB medications, but it’s important to underscore that, based on the FDA’s initial evaluation, the increased risk of cancer to patients with NMBA exposure appears to be the same for NDMA exposure but less than the risk from NDEA exposure,” FDA Commissioner Scott Gottlieb said in statement.

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As in the case of NDEA and NDMA, the FDA has told patients whose medications are on the list of recalled products containing NMBA that they may face higher risks from immediately stopping without any alternative treatment. It has counseled patients to continue to take them and contact their doctor.

Gottlieb said that the FDA is continuing extensive testing to see if even more nitrosamine impurities will pop up. He said it is “making important strides at understanding how these impurities form.” The agency is sharing its testing methods with drugmakers so they can be on the lookout as well.

“The FDA is committed to implementing measures to prevent the formation of these impurities during drug manufacturing processes in the future,” Gottlieb said.

The FDA has been aggressively trying to cleanse the drug supply of the impurities after they were first discovered in valsartan last summer, and since also in losartan and irbesartan. That, however, has also led to shortages. The FDA has said valsartan is in short supply and that it expects other sartan drugs to come up short as well.

The announcement of the newest danger came in fact on the same day that Aurobindo Pharma USA announced a recall to the consumer level of 38 lots of valsartan and amlodipine and valsartan tablets because they were found to contain NDEA.