On April 1, the Food and Drug Administration (FDA) urged companies to stop selling all forms of the heartburn drug Zantac after the agency concluded the product could cause cancer due to an agent that builds up when the drug is stored for long periods.

The agency also told consumers to stop taking over-the-counter varieties of the drug, called ranitidine, and throw out any liquids or tablets containing the product. The FDA said people who are prescribed the medication should consult with their doctors before stopping.

FDA recommendations follow concerns raised last fall

Most manufacturers withdrew products containing ranitidine after an online pharmacy company raised concerns over the drug beginning nearly one year ago. In September, the FDA said the contaminant in Zantac is found in a variety of products, including cured meats. Most pharmacies removed all ranitidine products from their shelves at that time.

The chemical is called N-nitrosodimethylamine, or NDMA, which is believed to cause cancer in humans. Concerns were raised after online pharmacy Valisure began testing drugs it sells for NDMA, and ranitidine was one of the first it tested. The company speculated the contaminant resulted due to the instability of the ranitidine molecule, which can degrade when subjected to high temperatures.

FDA seems to confirm Valisure findings

At first, the FDA was at odds with the company’s findings, saying they were invalid because Valisure heated the product and created higher levels of NDMA. However, the agency’s recent announcement seems to align with the company’s results showing consumers remain at high risk.

Valisure is still researching the drug, trying to determine the possible long-term effects of the contaminant. The FDA, meanwhile, says heartburn sufferers can consider other products that do not contain NDMA, such as Prilosec, Prevacid, Nexium, Pepcid and Tagamet.