The Walgreens and CVS pharmacy chains have stopped selling heartburn medicine Zantac and its generic versions after the Food and Drug Administration warned this month that it had detected low levels of a carcinogenic drug in samples of the drug.
A Walgreens spokesman said in a statement Monday that the company had withdrawn the drug from its shelves "while the FDA continues its review of the products."
Walgreens and CVS, which announced the move on Saturday, both noted that the substance, known as ranitidine, has not been recalled. The companies said that customers who had purchased the products could return them for a refund.
Zantac, the brand-name version of the drug, is sold by Sanofi, but generic versions are widely sold.
This month, drug manufacturer Novartis said that its generic drug division, Sandoz, had stopped distributing a prescription form of ranitidine worldwide while investigating the F.D.A.'s findings. GlaxoSmithKline has also stopped shipping its generic version of the drug, as well as Dr. Reddy's Laboratories, a major generic manufacturer.
The companies, including Sanofi, have stopped remembering their products in the United States. In a statement on Monday, Sanofi said that the levels of pollution that F.D.A. had found in "preliminary tests barely exceed the amounts found in regular foods."
The company added: "We work closely with F.D.A. and conduct our own robust surveys to ensure that we continue to meet the highest quality safety and quality standards. ”
Apotex, which makes store-branded versions of Zantac for Walgreens, Walmart and Rite-Aid, remembered its ranitidine last week products.
In his September 13 warning, the F.D.A. said it had found low levels of a cancer-causing contaminant, a type of nitrosamine called nitrosodimethylamine, or NDMA, in heartburn medication.
Nitrosamines can cause liver tumors and other organs in lab animals, and are believed to be carcinogenic in humans. NDMA can be formed during production if the chemical reactions used to prepare the substance are not carefully controlled, F.D.A. said.
Ranitidine is a histamine blocker that works to lower the acid created in the stomach, according to F.D.A. The medication is sometimes prescribed to prevent stomach ulcers and intestines as well as gastroesophageal reflux disease, the agency says.
CVS said it would continue to sell other histamine blockers, including Pepcid, Tagamet and the generic equivalents famotidine and cimetidine.
Katie Thomas contributed reporting.