American reseller CVS has become the latest to stop the sale of a heartburn drug being investigated for cancer links.
There are concerns in several countries about the presence of impurities in Zantac and other ranitidine products.
Canada and France have already announced Zantac swings. The US and the European Union are investigating.
Health authorities say there is no immediate risk, but patients have been advised to consult a physician who can prescribe alternatives to ranitidine.
What is the fear of?
On September 1[ads1]3, both the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) published their decisions to assess the presence of N-nitrosodimethylamine (NDMA) in medicines containing the drug ranitidine.
NDMA is classified as a probable carcinogen (a substance that can cause cancer) on the basis of animal studies.
NDMA is found in water and foods, including meat, dairy products and vegetables, but is not expected to cause damage if consumed at very low levels, EMA says.
Ranitidine products are used to reduce the production of the stomach. acid in patients with conditions such as heartburn and stomach ulcers.
They are available over the counter, and by prescription.
Who has remembered the products so far?
CVS's announcement on Saturday said it suspended sales of Zantac and CVS Health brand ranitidine products "out of an abundance of caution".
"Zantac brand products and CVS brand ranitidine products have not been recalled, and the FDA does not recommend that patients stop taking ranitidine at this time," the company said.
Walgreens, Walmart and Rite Aid in the United States had previously made a similar decision.
Canada and France have removed the drugs from the pharmacy shelves. A number of other countries have followed suit.
Drug manufacturers also recall products containing NDMA.
Sandoz, owned by Novartis, told the BBC that it recalled "several batches of its ranitidine-containing drugs". The recalls were "in progress or pending" in Australia, Austria, Belgium, Canada, Croatia, Czech Republic, Denmark, Finland, Germany, Hungary, Macedonia, Portugal, Slovakia, Slovenia, Sweden, Switzerland and the United States.
Apotex also said it remembered ranitidine tablets in the United States.
The BBC has approached GlaxoSmithKline – original manufacturers of Zantac. The company is reported to have stopped distributing its generic version of the drug and recalled its products from India and Hong Kong.
What should patients do?
Health authorities urge people taking ranitidine not to interrupt it immediately.  However, the FDA said that those who prescribe it should contact health professionals about alternatives. And those who buy it without a counter can consider other options.
French authorities also emphasized that there was no "acute risk" and patients should not stop the medication or return it to the pharmacy.