Pfizer has recalled its popular anti-smoking drug Chantix after it was found to contain high levels of cancer-causing agents called nitrosamines.

According to a notice posted on the Food and Drug Administration's (FDA) website Thursday, the drug maker is 'voluntarily recalling all lots of Chantix 0.5mg and 1mg tablets to the patient level due to the presence of a nitrosamine, N-nitroso-varenicline (NDMA), at or above the FDA interim acceptable intake limit'. 

Then, in an update posted on Friday, the FDA advised 'patients taking recalled varenicline to continue taking their current medicine until their pharmacist provides a replacement or their doctor prescribes a different treatment'. 

'The health benefits of stopping smoking outweigh the cancer risk from the nitrosamine impurity in varenicline,' it added. 

Pfizer paused distribution of Chantix back in July after finding elevated levels of nitrosamines in the pills and announced it was recalling 12 lots of the anti-smoking drug.  

The drug giant - currently best known for its COVID vaccine - insisted there was no immediate risk to patients taking this medication' and said the recall is out of an abundance of caution. 

In the past the US drug regulator has reached out to companies whose drugs had NDMA over accepted levels.

Chantix was approved by the FDA in May 2006 as a prescription medication which helps adults aged 18 and over quit smoking and is used for 12 to 24 weeks.