FDA investigating whether Zantac causes carcinogens to form in users

NEW YORK (Reuters) – The U.S. Food and Drug Administration is investigating whether the popular heartburn drug Zantac causes carcinogens to form in the bodies of users, in an effort to fully understand the risks posed by the already recalled drug, the agency’s spokesman said on Thursday.

The issue of whether ranitidine, commonly known as Zantac, causes levels of the probable carcinogen N-nitrosodimethylamine (NDMA) to rise in users’ bodies has been raised previously by Valisure, an online pharmacy that originally flagged the potential contamination of ranitidine to the FDA.

Zantac, sold over-the-counter in the United States by French drugmaker Sanofi SA (SASY.PA), and some of its generic versions, have been recalled due to possible NDMA contamination of pills that had not yet been consumed. The FDA said earlier this month it found unacceptable levels of NDMA in drugs containing ranitidine.

But FDA spokesman Jeremy Kahn said the regulator is now “working to understand what happens to NDMA levels in the body, after ranitidine has been exposed to acid in the stomach.”

Zantac has been on the market for more than 35 years and was originally sold by Glaxo Holdings Ltd, now a part of GlaxoSmithKline PLC. (GSK.L) At one point it was the top-selling drug in the world.

Representatives of GSK and Sanofi were not immediately available for comment.

Valisure’s Chief Executive David Light said it was important that the FDA is investigating the issue because the company’s data suggests the NDMA levels that can be formed in the body “are many magnitudes of order higher than what’s been talked about in the contamination.”

“This is one of the main red flags we’ve raised the whole time — not just contamination but the fact that this is happening in the human body,” Light said.

Sanofi said last week it would recall the drug in the United States and Canada. Other drugmakers including GlaxoSmithKline and Novartis (NOVN.S) have recalled or halted distribution of their versions of the drug.

Retailers including Walmart Inc (WMT.N), CVS Health Corp (CVS.N), Walgreens Boots Alliance Inc (WBA.O) and Rite Aid Corp (RAD.N) have stopped selling ranitidine.

The FDA said on Wednesday that early tests of alternatives to Zantac such as Pepcid, Tagamet, Nexium, Prevacid and Prilosec have not been found to contain NDMA.

NDMA had previously been found in some blood pressure medicines from a class of drugs known as angiotensin II receptor blockers. Those impurities are believed to have been introduced by recent changes in the manufacturing process.