June 25, 2021 -- Pfizer is suspending distribution of the anti-smoking treatment Chantix after heightened levels of the carcinogen N-nitrosodimethylamine (NDMA) were found in some lots of the pills.

The pharmaceutical company is also recalling some lots of Chantix that may have high levels of NDMA, Reuters reported.

Pfizer told Reuters the distribution pause was ordered out of abundance of caution while further testing is conducted. The FDA approved Varenacline, which is marketed as Chantix, in 2006.

"The benefits of Chantix outweigh the very low potential risks, if any, posed by nitrosamine exposure from varenicline on top of other common sources over a lifetime," Pfizer spokesperson Steven Danehy said in an email, according to Reuters.

The FDA has not issued a recall on Chantix. In Canada, however, health authorities on June 8 instituted a recall for Champix, the name under which the drug is sold in that nation.

The Chantix website says it’s a three-to-six-month treatment that helps people overcome the need to smoke tobacco. The website says more than 13 million people have been prescribed Chantix.

Other health concerns have been raised about Chantix, such as mental health side effects.

In 2016 ,however, researchers concluded Chantix did not appear to raise the risk of serious health disorders such as depression, anxiety, and suicidal thoughts.