Testing by the U.S. Food and Drug Administration (FDA) found that several batches of extended-release metformin contained “unacceptable” levels of N-Nitrosodimethylamine (NDMA).
NDMA is a toxic chemical that is believed to cause cancer in humans at high levels. It is particularly concerning in a daily medication like metformin, which is meant to be taken by patients every day for years.
The announcement is a major reverse-course for the FDA, which previously said in February that its tests did not find unacceptable levels of NDMA in metformin.
Those findings were challenged by the online pharmacy Valisure, which demanded recalls for metformin after their own tests found excessive levels of NDMA in metformin from 11 companies.
One batch of metformin made by Amneal Pharmaceuticals had over 16-times the daily limit for NDMA, according to Valisure.
Now, after months of additional testing, the FDA said it is contacting several unnamed drug-makers to take “quick and appropriate action,” which may include recalls for extended-release metformin.
The FDA said its tests on metformin’s immediate-release formula did not find high levels of NDMA.
NDMA contamination has already led to dozens of recalls for other medications, including all generic Zantac® and multiple blood pressure drugs. A growing number of lawsuits have also been filed against drug-makers by people with cancer.
Concerns about metformin were raised late last year, when Canada and Singapore recalled a small amount of metformin due to NDMA.
Metformin is a generic medication that is used to control blood-sugar levels in people with type-2 diabetes. It is the 4th most-prescribed drug in the U.S. Around 21 million prescriptions for extended-release metformin were written last year, according to Bloomberg.