GlaxoSmithKline and Sanofi face a Justice Department probe that is looking into what the drug makers knew about the risk of cancer from Zantac, and when it may have discovered that the main ingredient in the recalled heartburn drug concerns to the carcinogenic chemical byproduct N-nitrosodimenthylamine (NDMA).

Zantac (ranitidine) was aggressively marketed for decades as a safe and effective treatment for heartburn, including both prescription and over-the-counter versions of the treatment, which have generated billions in sale. However, after an independent pharmacy discovered late last year that pills contained high levels of NDMA, Zantac recalls have been issued for most versions of the medication.

NDMA used to be a chemical byproduct of making rocket fuel in the early 1990s. However, today, its only use is to cause cancer in animals as part of laboratory experiments.

In filings to the Securities and Exchange Commission (SEC), Sanofi and GlaxoSmithKline announced they are under investigation by the Department of Justice.

“On 18 June 2020, the Group received a Civil Investigative Demand (CID) from the US Department of Justice (DOJ) seeking information related to Zantac pursuant to the False Claims Act,” GlaxoSmithKline wrote in it’s Q3 report to the SEC. “The Group is co-operating with the DOJ to provide this information. Additionally, on 18 June 2020, the New Mexico Attorney General filed a lawsuit against multiple defendants, including GSK, relating to Zantac and other products containing ranitidine.”

Reports indicate that the DOJ is investigating whether the companies failed to adequately inform regulators about the potential presence of the known carcinogen in Zantac.

While FDA standards have established that maximum human daily exposure to NDMA should be only 96 nanograms, testing by the independent pharmacy Valisure found some 150 mg Zantac pills contained more than 3 million nanograms of NDMA. Exposure to the Zantac ingredient has been linked to reports of breast cancer, kidney cancer, leukemia and other cancers, raising widespread concerns among long-term users of the drug.

Valisure is an independent online pharmacy that tests drugs thoroughly before sending them to customers. In September 2019, the pharmacy filed a citizen’s petition with the FDA, calling for Zantac recalls after detecting high levels of N-Nitrosodimethylamine (NDMA) in every batch of Zantac it tested.

After determining there was no way to reliably determine which pills were contaminated, the FDA decided all manufacturers must issue Zantac recalls for ranitidine-based drugs on April 1, decades after the drugs were introduced and after millions of Americans were exposed to the chemicals which may have caused the development of breast cancer, testicular cancer, kidney cancer, bladder cancer and other injuries.

Hundreds of Zantac lawsuits are now being pursued throughout the United States by former long-term users of the medication who indicate they have developed cancer from the heartburn drug. However, it is widely expected that tens of thousands of claims will eventually be involved in the litigation, given the widespread use of the medication.

To deal with the increasing complaints being filed throughout the federal court system, the U.S. Judicial Panel on Multidistrict Litigation recently ordered all Zantac claims be centralized and consolidated in the U.S. District Court for the Southern District of Florida, where the litigation will be overseen by U.S. District Judge Robin L. Rosenberg during coordinated discovery and pretrial proceedings.