The metformin recalls are coming fast and furious, now that the U.S. Food & Drug Administration has confirmed the presence of a probable carcinogen in some versions of the widely used Type 2 diabetes drug.
The FDA began investigating contaminated metformin late last year after Singapore authorities discovered that some tablets contained excessive levels of N-Nitrosodimethylamine (NDMA), a probable human carcinogen. Although the agency’s own tests did find NDMA in metformin sold in the United States, the regulator maintained that the levels detected were far below its recommended daily limit of 96 nanograms.
That all changed this past April when the online pharmacy Valisure reported that its own testing program had detected excessive levels of NDMA in 16 of 38 metformin samples tested. Because Valisure is the same company that discovered high levels of NDMA in Zantac, its metformin findings caused quite a stir.
Two months later, further FDA testing confirmed excessive levels of NDMA in some extended-release metformin product and initially asked five drug makers to remove their medications from the market. Since then, metformin ER recalls have been announced by the following companies:
NDMA is classified as a probable human carcinogen based on animal tests that suggest exposure to high levels may increase the risk for cancer, including kidney, liver, gastrointestinal, and breast cancer.
The FDA began testing drugs for the compound shortly after NDMA turned up in generic versions of valsartan and other “sartan” blood pressure medications, resulting in dozens of recalls.
Last fall, the agency began investigating the presence of NDMA in brand-name and generic versions of Zantac. The agency ultimately requested that all versions of the heartburn medication be removed from the market entirely after confirming that the amount of NDMA in Zantac can increase over time.
Only extended-release metformin tablets in doses of 500 to 750 mg are affected by these recent recalls. Immediate-release tablets have not been found to contain high levels of NDMA.
Even if you have metformin tablets that appear on the recall list, it’s important to keep taking them until you can get a new prescription or alternative form of treatment for glucose management from your doctor. It could be dangerous for patients with Type 2 diabetes to stop taking their metformin without first talking to their health care professional.