Valisure, an online pharmacy and analytical laboratory based in New Haven, Conn., has asked the U.S. Food and Drug Administration to request recalls of the diabetes drug metformin from 11 companies after its own testing found levels of the probable carcinogen N-nitrosodimethylamine (NDMA) exceeded those recognized by the agency as being safe, according to a petition filed with the FDA.
“The presence of this probable carcinogen in a medication that is taken daily by adults and adolescents for a chronic condition like diabetes, makes [these findings] particularly troubling,” the pharmacy said in the petition. It noted that NDMA is classified by the World Health Organization and the International Agency for Research on Cancer as a Group 2A compound, meaning that it is “probably carcinogenic to humans.”
The Valisure findings are in contrast to those from the FDA’s own testing of metformin from eight companies. In results released Feb. 2, the agency found no NDMA in metformin from seven of the companies, and elevations within the safe limit in metformin from the remaining company. Based on those results, the FDA did not issue a recall.
The FDA declined to comment on the petition, pending a formal written response, a spokesman said.
Valisure said in its petition that one reason it found NDMA at concerning levels, and the FDA did not, could be that the pharmacy’s testing was more thorough than the agency’s because it had used its proprietary analytical technologies in addition to FDA standard assays. The pharmacy said it also cast a wider net, testing samples from 22 companies instead of 8, as the FDA had.
“At least one company that consistently displayed high levels of NDMA in all Valisure-tested batches was a company whose metformin products, to Valisure’s knowledge, were not tested by FDA,” Valisure said in the petition.
The pharmacy tested 38 batches of metformin from 22 companies, and found 16 contaminated batches from 11 companies. Results from one company were confirmed by an independent laboratory in California.
In addition, “there was significant variability from batch to batch, even within a single company, underscoring the importance of batch-level chemical analysis and the necessity of overall increased quality surveillance of medications,” the pharmacy stated in the petition.
David Light, Valisure founder and CEO, said in a press release that the results “indicate that contaminated batches of drugs are scattered and intermixed with clean [batches] throughout the American pharmaceutical supply chain. This strongly suggests that neither the limited testing FDA is able to conduct nor the pharmaceutical companies’ self-reporting of analytical results is sufficient to protect American consumers.”
He explained in an interview that metformin contamination probably comes from poor manufacturing, as NDMA can form during the manufacturing process. Companies are supposed to have processes in place to limit its formation and to check for and remove it before products are shipped. The contaminated batches might have come from China, which makes the bulk of U.S. active pharmaceutical ingredients, he said.
Recently, Apotex and Ranbaxy Pharmaceuticals recalled specific metformin lots in Canada after Canadian health authorities requested NDMA testing. Metformin versions have also been recalled in Singapore. European health authorities are also looking into the issue, according to a Mar. 3 press release from the European Medicines Agency.
Over the past 2 years, NDMA contamination has led to recalls of angiotensin receptor blockers, such as valsartan and losartan, because of NDMA in excess of the daily limit, and ranitidine-containing products such as Zantac. Valisure said it hopes the FDA will avoid the “year-long rolling recalls” that have occurred for angiotensin receptor blockers.
Metformin, which is used to treat type 2 diabetes, is the fourth-most prescribed drug in the United States. About 80 million prescriptions were written for it during 2019, according to the press release.
Valisure launched its investigation after it found NDMA in metformin a client asked it to check.