The online pharmacy Valisure is asking U.S. regulators to recall metformin diabetes drugs made by 11 companies after tests found excessive levels of NDMA, a cancer-causing chemical.
NDMA (N-Nitrosodimethylamine) and similar chemicals, collectively known as “nitrosamines,” are toxic chemicals that are considered probable human carcinogens.
NDMA contamination has already prompted dozens of recalls for blood pressure drugs such as valsartan and losartan, as well as heartburn drugs such as Zantac® and ranitidine.
Metformin is the 4th-most-prescribed drug in the U.S., with approximately 80 million prescriptions written in 2019. It controls high blood sugar levels in people with type-2 diabetes.
On February 3, FDA tests found no NDMA, or only extremely low levels, in 16 batches of metformin from 7 companies. At the time, the FDA did not recommend any recalls.
However, when Valisure tested 38 batches of metformin from 22 companies, 42% tested positive for NDMA contamination above the FDA’s acceptable daily intake level of 96-ng.
Valisure is recommending recalls for 16 batches of metformin from 11 companies that revealed NDMA levels above the 96ng daily limit.
Several batches tested by Valisure contained more than 10-times the daily acceptable intake limit for NDMA. Valisure also found significant variability from batch to batch, even within a single company.
The highest amount of NDMA was found in a batch of metformin manufactured by Amneal Pharmaceuticals LLC, which contained 16.5-times the daily acceptable intake level of NDMA.
Metformin has not been recalled in the U.S. for NDMA contamination, but several recalls have been issued in Singapore and Canada.
Valisure warned that the cancer risk from NDMA is particularly concerning for a drug like metformin, because metformin is taken multiple times a day for the lifespan of a patient with type-2 diabetes.