(CNN) - The US Food and Drug Administration issued a warning letter to the Chinese maker of an ingredient in popular heart drugs and said it continues to test the ingredient for cancer-causing chemicals.
The letter, sent in late November, details manufacturing violations at the facility of Zhejiang Huahai Pharmaceutical Co. Ltd., pointing out cross-contamination from one line to another, control issues and impurity control problems.
"These violations reveal a disturbing lack of oversight at this API manufacturer that puts patients at risk," FDA Commissioner Dr. Scott Gottlieb said in a statement.
Zhejiang Huahai Pharmaceutical Co. is also on an import alert. The FDA made it illegal to bring in any API drugs -- active pharmaceutical ingredient drugs -- made by that company in September.
Tests this summer found that cancer-causing contaminants was accidentally added to certain drugs that are used to prevent heart problems and high blood pressure. The contaminants first showed up in drugs that contained valsartan, but subsequent tests have found them in others made by the company, like losartan and potassium and hydrochlorothiazide. Since July, several companies that use Zhejiang Huahai's ingredients have recalled their products.
The FDA keeps a list of drugs that are subject to the recall, and because there are so many drugs affected by this recall, there's a separate list with drugs that haven't been recalled. The list was last updated December 4.
Tests found that the drugs were contaminated with NDMA or NDEA. The FDA said Wednesday that it updated its testing methods to look for both.
N-Nitrosodiethylamine or NDEA is a suspected human and animal carcinogen that is used in gasoline as a stabilizer for industry materials and as a lubricant additive, according to the National Institutes of Health.
NDMA, N-nitrosodimethylamine, is an impurity that is also considered a possible carcinogen by the US Environmental Protection Agency.
NDMA is an organic chemical used to make liquid rocket fuel and is a byproduct of manufacturing some pesticides and processing fish. It can be unintentionally introduced into manufacturing through certain chemical reactions.
The FDA is testing all heart drugs known as angiotensin II receptor blockers or ARBs for these impurities.
If your drug is on the recall list, the FDA suggests taking it until your doctor or pharmacist provides a replacement. Because not all valsartan and irbesartan drugs are involved in the recall, you might be able to switch to another company's version.
It's unclear exactly what the cancer risk is if you take the contaminated pills; the FDA believes that the risk is low.
It estimated that if 8,000 people took the highest dose of valsartan (320 milligrams) containing NDMA from these recalled batches daily for four years, there may be one additional case of cancer over their lifetimes. Many patients take a much lower dose of valsartan, and therefore their risks are theoretically much lower.
The FDA said it will continue to test all products containing valsartan and similar drugs for the presence of impurities.
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