According to the notice posted on the Food and Drug Administration website, the recall is for all lots of 0.5 mg and 1 mg varenicline tablets.
The recall notice says that long-term ingestion can lead to a "potential increased cancer risk in humans, but there is no immediate risk to patients taking this medication."
The FDA said in an update Friday that patients should "continue taking their current medicine until their pharmacist provides a replacement or their doctor prescribes a different treatment."
Pfizer recalled some lots of the smoking cessation treatment in July and expanded the recall to additional lots in August.
The recalled drugs were distributed nationwide to wholesalers and distributors in the US, Virgin Islands and Puerto Rico from May 2019 to September 2021.
The FDA acknowledged the ongoing recall could cause a drug shortage and said to lessen the impact to patients, it will "not object to certain manufacturers distributing varenicline tablets containing N-nitroso-varenicline above FDA's acceptable intake limit of 37 ng per day but below the interim acceptable intake limit of 185 ng per day until the impurity can be eliminated or reduced to acceptable levels."
The agency said the "health benefits of stopping smoking outweigh the cancer risk from the nitrosamine impurity in varenicline."