Genotoxic impurities in drugs, known as nitrosamines, have been the topic of an ongoing FDA investigation. N-Nitrosodimethylamine, also known as NDMA, as a type of nitrosamine that is a known environmental contaminant. It has been classified as a probable human carcinogen. NDMA has been found in water and foods, including dairy products, vegetables and grilled and cured meats. In an official statement, the FDA announced that NDMA was found in a diabetes drug — Metformin.

According to the statement, the acceptable daily intake limit for NDMA in the U.S. is 96 nanograms. While the impurities were found in Metformin outside of the United States, the FDA is still investigating whether Metformin in the U.S. is also contaminated.

Janet Woodcock, M.D., director of the FDA’s Center for Drug Evaluation and Research, said in a statement “Our investigations, including our current investigation of metformin, take into account the medical necessity of the drug, how many Americans may take it, and whether there may be alternative treatments available. The American public can expect that we will act quickly to address any issue as soon as we find out about it.”

Woodcock noted that improved technology allows the agency to detect impurities in drug products. Several other drug products, including angiotensin II receptor blockers and ranitidine (Zantac) have also been found to contain small amounts of nitrosamines, resulting in recalls.

Woodcock added, “The FDA recommends prescribers continue to use Metformin when clinically appropriate, as the FDA investigation is still ongoing, and there are no alternative medications that treat this condition in the same way.”

For a list of the affected products, click here.

This isn’t the first time Metformin has made headlines.  Researchers from Albert Einstein College of Medicine in New York City used data from the Diabetes Prevention Program and the Diabetes Prevention Program Outcomes Study to look into the effects of metformin use on vitamin B12 levels. They found that nearly 20% of those taking Metformin had borderline low vitamin B12 levels compared to 10% of those taking a placebo.