Other blood pressure pills containing losartan and irbesartan are still available.
Dr June Raine, chief executive of the MHRA, said: ‘Patient safety is our watchword.
‘We’re recalling batches of certain sartan-containing as precautionary measure while we continue our investigation.
‘It’s important that healthcare professionals check their stock to quarantine and return these batches.
‘If you’ve been taking one of the affected products, speak with your doctor or pharmacist before stopping any treatment – they can address any concerns and can advise you on the best course of action.’
Officials have yet to explain how the impurity may have occurred. They are often caused by contamination in factories or brought on during the manufacturing or storage process.
Exposure to light, temperatures or even reactions with the container that holds the drug can trigger chemical changes.