The company announced that Chantix consumers are exposed to the chemical nitrosamines, commonly found in water and foods, in a press release announcing its decision last week.
"These impurities may increase the risk of cancer if people are exposed to them above acceptable levels over long periods of time," the company said.
The U.S. Food and Drug Administration alerted consumers, patients and health care professionals about the voluntary recall on July 2, weeks ahead of the company's official announcement.
Chantix tablets specifically identified in the recall include the following lot numbers: 00019213, EC6994, EA6080, EC9843, 00020231, 00020232, 00020357, 00020358, 00020716, ET1600, ET1607 and ET1609.
The levels of nitrosamines in Chantix exceed the FDA's standards, but the agency said it believes there is "no immediate risk to patients taking this medication."
The FDA said the pause was made out of an abundance of caution, but is not objecting to certain manufactures temporarily distributing Chantix tablets amid the recall announcement.
"An increased cancer risk would be associated with long-term use, and the health benefits of stopping smoking outweigh the cancer risk from the nitrosamine impurity in varenicline (Chantix)," the FDA said.
Chantix was approved by the FDA as an anti-smoking prescription medication for adults age 18 or older in 2006.
Pfizer says patients typically use the drug during a span of 12 to 24 weeks.