© Getty Images/KJN
Pfizer recalled its anti-smoking drug Chantix due to high levels of an ingredient that is tied to an increased risk of cancer.

In a notice posted to the Food and Drug Administration's (FDA) website on Thursday, Pfizer said it was recalling Chantix 0.5 mg and 1 mg tablets to the consumer level due to the presence of N-nitroso-varenicline.

Long term ingestion of N-nitroso-varenicline can be associated with a "theoretical potential increased cancer risk in humans," the notice said. However, there is no immediate risk to patients taking the drug.

The company said it is undertaking the recall as a precautionary measure, adding that the benefits of stopping smoking "outweigh the theoretical potential cancer risk from the nitrosamine impurity."

The company is recalling all lots of the drug that were distributed to wholesalers and distributors in the U.S., US Virgin Islands, and Puerto Rico from May 2019 to September.

In a Friday update, the FDA said patients should continue taking their medicine until their pharmacists provides a replacement or their doctors prescribe a different treatment.

N-nitroso-varenicline is a nitrosamine, which are common in water and foods.

Everyone is exposed to nitrosamines at some level. However, they may increase the risk of cancer if people are exposed above a certain limit.

Pfizer previously recalled 12 lots of Chantix in July due to the presence of N-nitroso-varenicline. Last month, it recalled four additional lots due to the impurity.