FDA Investigating Diabetes Drug Metformin for Traces of Cancer-Linked Chemical NDMA

The U.S. Food and Drug Administration (FDA) is investigating whether a drug used to treat diabetes is contaminated with traces of a chemical thought to increase the risk of developing cancer.

The federal agency is working with companies to test samples of metformin sold in the U.S. for the carcinogen N-Nitrosodimethylamine (NDMA), according to a statement from Dr. Janet Woodcock, the director of the FDA's Center for Drug Evaluation and Research. Levels above the daily intake of 96 nanograms are considered unsafe in the U.S.

Metformin, a prescription drug used to control blood sugar levels in type 2 diabetes patients, will be pulled from the market if high levels of NDMA are found.

"If as part of our investigation, metformin drugs are recalled, the FDA will provide timely updates to patients and healthcare professionals," Woodcock said.

She stressed: "Patients should continue taking metformin to keep their diabetes under control. It could be dangerous for patients with this serious condition to stop taking their metformin without first talking to their healthcare professional.

"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."

Woodcock stated some metformin diabetes medicines in other countries have been found to contain low levels of NDMA. The amounts detected outside the U.S. were "within the range that is naturally occurring in some foods and in water," said Woodcock.

Some regulatory bodies outside the U.S. have recalled metformin drugs, but the FDA currently has no similar plans, she said.

Woodcock assured "everyone is exposed to some level of NDMA," and said it is not thought to be harmful when ingested at low levels.

The organic compound is present in water and foods, including products such as dairy products, grilled and cured meats, and vegetables. NDMA can enter products in a variety of ways, such as during processing, packaging or storing.

"Genotoxic substances such as NDMA may increase the risk of cancer if people are exposed to them above acceptable levels and over long periods of time, but a person taking a drug that contains NDMA at-or-below the acceptable daily intake limit every day for 70 years is not expected to have an increased risk of cancer," said Woodcock.

She suggested advances in technology and testing methods mean even trace amounts of drug impurities can now be picked up, which "may be the reason why more products have been found to have low levels of NDMA."

Ranit Mishori, a professor of family medicine at Georgetown University, told Reuters: "If these reports are true, it could be a big blow to many millions of people on this drug.

"There are many other alternatives and other medication classes but many of them have side effects, are more expensive and some of the newest ones may not be covered by insurance."

The probe is part of wider efforts by the FDA to find nitrosamines in drugs. In September, the body discovered NDMA in common heartburn medications ranitidine, commonly known as Zantac, and nizatidine. Several companies, such as CVS and Aurobindo Pharma USA, have voluntarily stopped selling Zantac due to concerns around NDMA.

"We have launched an investigation to understand the cause of this impurity in these drugs and to provide information for patients and consumers who take them," the FDA said in a statement on Wednesday.

It advised consumers who take the drugs to limit their intake of foods containing nitrates, such as processed meats and preservatives like sodium nitrite, as evidence suggests "there may be a link between the presence of nitrites and the formation of NDMA in the body if ranitidine or nizatidine is also present."