FRANKFURT - European and North American regulators have said they are examining a second potentially cancer-causing substance in a commonly-used blood pressure drug made by Chinese firm Zhejiang Huahai Pharmaceuticals.
Statements from health regulators in the EU, United States and Canada add to concerns flagged earlier this year when the drug, valsartan, was found to contain traces of N-nitrosodimethylamine (NDMA), a probable human carcinogen, due to a production change in 2012.
The findings have already prompted recalls in more than 50 countries, affecting several Chinese and Indian companies.
On Thursday, the European Medicines Agency (EMA) said a similar impurity had been detected in products produced before 2012.
"In addition to NDMA, EMA is assessing the impact of a related substance, N-nitrosodiethylamine (NDEA), which has been detected in valsartan made by Zhejiang Huahai using its previous manufacturing process before changes were introduced in 2012," it said in a statement.
"Data on levels of NDEA are currently very limited, and EMA will provide further information on whether its presence impacts the risk assessment once more information becomes available."
The watchdog also said further risk assessment had confirmed that the life-time risk of cancer from exposure to levels of NDMA detected in valsartan was considered low.
The U.S. Food And Drug Administration (FDA) said the latest testing of products found NDEA in three lots of valsartan produced by Indian firm Torrent Pharmaceuticals that were recalled in August.
Torrent makes valsartan tablets using active pharmaceutical ingredients from Zhejiang Huahai. It first said it was recalling 14 lots of its tablets due to the presence of an unexpected carcinogenic impurity on August 17, but later expanded its recall to all lots within expiry.
Separately, Canada's health watchdog said that it too had found NDEA, but noted all drugs containing valsartan manufactured by Zhejiang Huahai had already been recalled in Canada after the first impurity was identified in the summer.
"Health Canada is working with the EMA, the U.S. FDA, and other international regulatory partners to determine the root cause of the issue and confirm that necessary actions are taken," it said in a statement.
Zhejiang Huahai did not answer Reuters' calls to request comment.
A Torrent Pharmaceuticals representative declined to comment.
(Reporting by Ludwig Burger, Tamara Mathias, Sharnya G, Tanvi Mehta and Shanghai newsroom; Editing by Thomas Seythal and Mark Potter)