The US Food and Drug Administration (FDA) has recommended voluntary recall of certain extended-release (ER) versions of metformin because testing has revealed excessive levels of N-nitrosodimethylamine (NDMA) in these products.
Metformin is the most commonly prescribed drug used to treat type 2 diabetes worldwide.
NDMA is a contaminant with the potential to be carcinogenic if there is exposure to above-acceptable levels over the long-term.
Five pharmaceutical firms in particular are being contacted by the FDA with notices (posted on the FDA website) recommending they voluntarily recall their products. At the time of writing, only one was listed, Apotex Corp and its metformin hydrochloride ER tablets, USP 500 mg.
The recall does not apply to immediate-release metformin products, the most commonly prescribed ones for diabetes, the agency stresses.
It also recommends that clinicians continue to prescribe metformin when clinically appropriate.
In late 2019, the FDA announced it had become aware of NDMA in some metformin products in other countries. The agency immediately began testing to determine whether the metformin in the US supply was at risk, as part of the ongoing investigation into nitrosamine impurities across medication types, which included recalls of hypertension and heartburn medications within the past 2 years.
By February 2020, the agency had identified very low levels of NDMA in some samples, but at that time, no FDA-tested sample of metformin exceeded the acceptable intake limit for NDMA, as reported by Medscape Medical News.
“Now that we have identified some metformin products that do not meet our standards, we’re taking action. As we have been doing since this impurity was first identified, we will communicate as new scientific information becomes available and will take further action, if appropriate,” Patrizia Cavazzoni, MD, acting director of the FDA Center for Drug Evaluation and Research, said in a press release.
Requests for recall apply only to affected products
The recall was instigated after the FDA became aware of reports of higher levels of NDMA in certain ER formulations of metformin through a citizen petition filed by a private laboratory. The agency confirmed unacceptable NDMA levels in some, but not all, of those lots.
“In other instances, our laboratory detected NDMA in lots that the private laboratory did not,” it notes.
The FDA says it is working closely with manufacturers of the recalled tablets to identify the source of the NDMA impurity and ensure appropriate testing is carried out.
Elevated levels of NDMA have been found in some finished-dose tablets of the ER formulations but NDMA has not been detected in samples of the metformin active pharmaceutical ingredient.
The FDA also stresses there are many other additional manufacturers that supply metformin ER products to much of the US market, and they are not being asked to recall their products.
Work is also ongoing to determine whether the drug recalls will result in shortages, and if so, the agency says it will collaborate with manufacturers to prevent or reduce any impact of shortages.
“We understand that patients may have concerns about possible impurities in their medicines and want to assure the public that we have been looking closely at this problem over many months in order to provide patients and healthcare professionals with clear and accurate answers,” Cavazzoni said.
For more information about NDMA, visit the FDA nitrosamines web page.
This article first appeared on Medscape.com.