Thailand's Food and Drug Administration (FDA) on Saturday issued an order to recall some batches of valsartan, a medicine used to control blood pressure and help prevent heart failure, after it was found some ingredients contain a carcinogenic impurity.
In doing so, Thailand has joined 22 countries in recalling the medicine, Wanchai Sattayawutthiphong, secretary-general of the FDA, said in a press statement on Saturday.
Valsartan is off-patent and is used as a component in other generic medicines.
In Thailand, Dr Wanchai said, the FDA found that out of seven companies licensed to manufacture valsartan, only two companies use pharmaceutical ingredients supplied by Zhejiang Huahai Pharmaceuticals. Dr Wanchai said that raw materials from this China-based manufacturer reportedly have been found to contain carcinogenic impurities.
The five formulas that will be withdrawn are Valatan 80 registered with the FDA under the drug formula No. 1A 9/54 (NG), Valatan 160 registered under the drug formula No. 1A 10/54 (NG), Valsarin 80 registered under the drug formula No. 1A 4/60 (NG), Valsarin 160 registered under the drug formula No. 1A 5/60 (NG) and Vasarin 320 registered under the drug formula No. 1A 6/60 (NG), he said.
The two pharmaceutical manufacturers have been ordered to complete the recall within 15 days.
The FDA has advised that consumers can return those medicines to the prescribing health care facilities, so that they can be destroyed, said Dr Wanchai.
Dr Wanchai also noted that the two pharmaceutical companies may be able to resume their production of valsartan-based formulas after they have resolved their problems with the use of potentially contaminated ingredients, he said.
The problem, he said, did not stem from the formula but ingredients.
Those patients using these drug formulas regularly won't then have to change to another formula, said Dr Wanchai.
The problem of impurity was discovered during tests on batches of active pharmaceutical ingredients (API) by The European Medicines Agency early this month.
The test found medicines from the supplier, Zhejiang Huahai Pharmaceuticals in Linhai, China contained N-Nitrosodimethylamine (NDMA), an organic chemical that is in a family of potent carcinogens.
The chemical has been used to make liquid rocket fuel, softeners and lubricants, among other products. It can also be unintentionally produced through certain chemical reactions and is a byproduct of some pesticide manufacturing, the making of rubber tires or fish processing.
Animal studies have shown that NDMA can be toxic and cause tumours in the liver, kidney and respiratory tract. It can also be potentially harmful to humans in certain quantities.
Exposure to high levels can cause liver damage and is a probable human carcinogen, according to the US Department of Health and Human Services.
European regulators said they were working together to investigate the extent of the issue.