The pharmaceutical chain has pulled the product and its store-branded alternatives after an FDA warning about the antacid’s key ingredient.

“CVS Pharmacy has suspended the sale of all Zantac brand and CVS Health brand ranitidine products until further notice,” the company said in a statement. “This action is being taken out of an abundance of caution due to a recent Product Alert from the U.S. Food and Drug Administration (FDA) that ranitidine products may contain a low level of nitrosodimethylamine (NDMA), which is a probable human carcinogen.”

The action by CVS follows similar decisions by Walgreens, Walmart and Rite Aid.

The moves come despite the fact that the FDA has not recalled Zantac or any brands that include ranitidine, nor has the agency recommended patients stop taking drugs with that ingredient. CVS, though, says it will offer refunds to anyone who purchased the drugs.

CVS says it will continue to sell other over-the-counter heartburn medications that do not use ranitidine, including Pepcid and Tagamet.

NDMA (N-nitrosodimethylamine) has been the basis of a number of recalls in blood pressure medicines over the past year. Right now, though, the FDA says it is still determining if the low levels of NDMA in Zantac pose a risk to patients.

Sanofi, the parent company of Zantac, defended the product earlier this month, telling Fortune “Sanofi takes patient safety seriously, and we are committed to working with the FDA. Zantac OTC (over the counter) has been around for over a decade and meets all the specified safety requirements for use in the OTC market.”

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