In the U.K., a Zantac contamination with a potential carcinogen has resulted in a recall.

Unfortunately, this isn’t the only heartburn drug subject to a recall due to possible contamination. Four others have also been recalled after reports that they may be tainted with the same probable human carcinogen — NDMA.

Zantac is used to treat heartburn, stomach ulcers, and gastrointestinal reflux disease (GERD). It is a histamine H2-receptor antagonist, and works by decreasing the amount of acid produced by the stomach, says GoodRx.

The drug is inexpensive and known by a number of brand names, including Pepcid, Famotadine, Axid, and others. Its generic name is ranitidine.

The U.S. Food and Drug Administration (FDA) issued an advisory about possible Zantac contamination, but the U.K. took more drastic measures, telling doctors not to prescribe the medication or its generic version, ranitidine, as a precaution intended to protect patients from harm.

The U.K. has recalled four versions of the drug, says the BBC. Reportedly, the drugs being recalled are:

• Zantac 150mg/10ml syrup
• Zantac 50mg/2ml injection
• Zantac 150mg tablets
• Zantac 300mg tablets

In addition, the drug’s maker has also instituted a voluntary recall with the hope of curbing the extent of the contamination.

Despite the recall, U.K. officials do not advise patients to stop taking the drug, because the risk associated with discontinuing a needed medication may be greater than the risk of taking a drug that’s possibly contaminated, according to the BBC. 

Zantac is believed to be contaminated with NDMA (N-nitrosodimethylamine). Researchers believe the naturally occurring chemical is a probable human carcinogen, a conclusion reached after lab tests indicated that it caused cancer in animals, according to livescience.com.

Zantac is not the only drug that has come under scrutiny for possibly contamination with NDMA. Valsartan, a drug used to treat high blood pressure, has been at the center of a similar debate since July 2018, because it also may have been contaminated with NDMA during the manufacturing process.

In the case of valsartan, investigators have said that the NDMA contamination likely occurred as an unintentional by-product during  the manufacturing process. Unfortunately, the problem was larger than initially thought, with valsartan produced around the world thought to have been contaminated. 

The problem seems to be even larger now, as other drugs, including Zantac, have been affected by a similar problem.

However, Harvard Health Publishing reports that while the FDA characterized the NDMA levels as “extremely high,” the testing was done applying high heat that “did not reflect typical conditions under which the medication would be stored or taken.” Harvard Health says the FDA is now asking drug companies to test their drugs at temperatures closer to human body temperature. 

Low levels of NDMA can be found in foods and water supplies, but higher levels like those in the Zantac contamination may be more concerning.