(Adds background, quote from Valisure, PIX available)
By Michael Erman
NEW YORK, Nov 1 (Reuters) - The U.S. Food and Drug Administration on Friday downplayed the risk caused by contamination of the already recalled popular heartburn drug Zantac, and said its tests suggest it does not cause carcinogens to form after ingestion by patients.
Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, said in a statement that the levels of the probable carcinogen N-nitrosodimethylamine (NDMA) it found in ranitidine - sold under the brand name Zantac - "are similar to the levels you would expect to be exposed to if you ate common foods like grilled or smoked meats."
Still, the FDA released results of its testing here on branded and generic ranitidine products that showed some versions of the over-the-counter medicine had as much as nine times the regulator's "acceptable limit" for NDMA.
The FDA said tests it ran to simulate how Zantac reacts in users' stomachs and small intestines suggest it does not cause NDMA to form there. The agency said it still plans to test the drugs in human patients to fully understand if NDMA forms after ingestion.
Zantac, sold in the United States by French drugmaker Sanofi SA, and some generic versions of the treatment have been recalled due to possible NDMA contamination. The FDA had said in October it found unacceptable levels of NDMA in drugs containing ranitidine.
The theory that ranitidine causes NDMA to form in patients bodies had previously been raised by Valisure, an online pharmacy that originally flagged the potential contamination to the FDA.
Valisure Chief Executive David Light in a statement criticized FDA testing methods as "overly simplistic conditions that do not properly evaluate a real-world stomach" and urged the agency to completely recall ranitidine and a similar drug, nizatidine.
Retailers including Walmart Inc, CVS Health Corp , Walgreens Boots Alliance Inc and Rite Aid Corp have stopped selling Zantac and generic ranitidine.
The FDA said last week that early tests of alternative heartburn treatments such as Pepcid, Tagamet, Nexium, Prevacid and Prilosec have not found NDMA.
NDMA had previously been found in some blood pressure medicines from a class of drugs known as angiotensin II receptor blockers (ARBs). Those impurities are believed to have been introduced by recent changes in the manufacturing process. (Reporting by Michael Erman Editing by Jonathan Oatis and Bill Berkrot)