FDA Finds Carcinogen in Some Versions of Metformin
On May 27, 2020, the FDA announced certain extended-release (ER) versions of metformin tested positive for unsafe levels of N-Nitrosodimethylamine (NDMA). Metformin was recalled in both Singapore and Canada this last year because of the same concerns with NDMA contamination.
The World Health Organization classifies NDMA as a probable human carcinogen. Exposure to NDMA has been linked to a number of cancers and even small amounts of exposure can lead to liver damage. The EPA classifies NDMA as a B2 carcinogen, meaning it has a sufficient amount of animal data to conclude that it’s a potential carcinogen for humans.
This comes after Valisure Phamacy filed a petition with the FDA in March 2020 that it found high levels of NDMA in certain batches of metformin - requesting the agency to recall the contaminated products. They reported that out of 128 samples they tested distributed in the US, 36% contained levels of NDMA that exceeded daily acceptable limits set by the FDA.
Metformin would be the third widely used medication in recent years to face recalls related to NDMA – after the chemical was found in dozens of shipments of blood pressure and heartburn drugs last year, triggering recalls of Zantac (ranitidine), valsartan and losartan.
Apotex Corp has made their recall public. The FDA announcement did not name the other four drugmakers who have been requested to recall their products but are working with the manufacturers to determine the appropriate next steps. It is unknown whether the recalls will lead to shortages of metformin, since there are a number of companies that make generic versions of the drug.
As information becomes available, pharmacies will be notified. Never discontinue your medication without first talking with your doctor. The FDA recommends that patients should continue taking metformin drugs until their doctor can prescribe a replacement, if necessary, as there can be considerable risks in stopping medications and experiencing high blood sugar levels.
Your pharmacy will automatically substitute any future refills with a safe manufacturer. If you have any concerns in the meantime, your pharmacist and/or prescriber should be able to work with you on an alternative option. There are safe extended-release formulations still available and there have been no reported contamination problems with immediate-release metformin.
Another consideration is if you take other oral diabetes medications (such as Invokana, Farxiga, Jardiance, Januvia, etc), there are combination options available that include Metformin in the same tablet … such as InvokaMet or JanuMet. These combination products have not had any reports of unsafe NDMA levels and have the added convenience of taking less pills in a day.
Read more information about Metformin benefits and risks here.