The Food and Drug Administration said on Friday that it had detected low levels of a cancer-causing contaminant in samples of heartburn medicines containing the drug commonly known as Zantac.
It was advising patients who take over-the-counter versions to consider switching to a different medication.
But no recalls have been initiated, and the agency said patients who take prescription versions of the drug, known as ranitidine, should consult with their doctors before stopping. The European Medicines Agency is also looking into the issue.
Zantac, the brand-name version of the drug, is sold by Sanofi, but generic versions are widely sold. The F.D.A. has not identified any specific products that were affected.
A spokeswoman for Sanofi said the company does not plan to recall the product.
“Sanofi takes patient safety seriously, and we are committed to working with the F.D.A.,” the spokeswoman, Ashleigh Koss, said in a statement. The over-the-counter version of Zantac “has been around for over a decade and meets all the specified safety requirements for use in the O.T.C. market.”
A trade group for over-the-counter drug manufacturers, the Consumer Healthcare Products Association, noted that the F.D.A. had not called for recalls, and that products containing the drug “play an important role in helping consumers manage their symptoms and treat heartburn.”
The contaminant, a type of nitrosamine called N-nitrosodimethylamine, or NDMA, is the same one that was found in some versions of valsartan, a blood-pressure drug carrying the brand name Diovan. The discovery of NDMA in valsartan led to several recalls of the commonly prescribed drug, which in turn led to supply shortages.
The valsartan recalls have renewed questions about the safety of the American drug supply, particularly of generic drugs, composed of raw ingredients that are frequently manufactured in countries like China and where F.D.A. oversight has lagged.
“I think this is another good example of how our regulations need to change,” said Dinesh Thakur, a drug-safety advocate who exposed widespread quality problems as a former executive at the Indian drug maker Ranbaxy Laboratories. He said the F.D.A.’s testing is too lax. “Things like this will never get caught, unless somebody is actually actively looking for stuff.”
Nitrosamines can cause tumors in the liver and other organs in lab animals, and are believed to be carcinogenic in humans. NDMA can form during manufacturing if the chemical reactions used to make the drug are not carefully controlled and monitored, the F.D.A. has said.
Jeremy Kahn, an agency spokesman, said Friday that the agency is still investigating contamination of the heartburn drugs, and that it is unclear how many companies’ products are affected and how the problem originated. However, he said, “We tested a small number of products for this impurity, and all of the products we’ve tested so far have had NDMA at low levels.”
He said that the levels were not high enough that the agency was recommending recalls so far, noting that low levels of NDMA are also found in other drugs and in food products. The agency first learned that some samples of ranitidine contained the chemical in June, after it tested the product in the wake of the valsartan recalls.
The agency’s announcement came on the same day that an online pharmacy, Valisure, petitioned the F.D.A. to request a recall of all products containing ranitidine, because it said its own tests had revealed high levels of NDMA, above the F.D.A.’s acceptable daily limit. The Valisure petition speculated that the source of the NDMA was the result of the “inherent instability” of the ranitidine molecule, which can degrade under certain conditions, such as when it is digested, to create NDMA.
“Our feeling is that this is extremely troublesome,” said David Light, the chief executive of Valisure, which is based in Connecticut. “We took it off our formulary right away.”
Mr. Kahn said the agency does not yet know whether the NDMA was a result of the instability of the drug, but he did say that the F.D.A. believed the source of the problem was separate from the ones that arose in the valsartan case.
The source of the contaminated valsartan was a Chinese manufacturer, Zhejiang Huahai Pharmaceutical Company. Major Pharmaceuticals, Teva Pharmaceutical Industries and Solco Healthcare, which is owned by Huahai Pharmaceutical, sold it in the United States.
The same type of impurities were later found in two other blood-pressure drugs, irbesartan and losartan, in the same class as valsartan. Two more nitrosamines — nitrosodiethylamine, or NDEA, and N-Nitroso-N-methyl-4-aminobutyric acid, or NMBA — were found in the drugs. Lists of the affected products are posted on the F.D.A. website.
In March, the F.D.A. approved a new version of generic valsartan to relieve the shortage, and the companies that recalled their products have begun returning versions of the drug that are not contaminated to the market, Mr. Kahn said.
More Coverage of Drug Contamination
New Generic Blood Pressure Drug Is Approved to Relieve ShortagesMarch 12, 2019
Blood Pressure Medicine Is RecalledJuly 16, 2018