A new international study suggests Chantix may increase the risk of heart attacks and other serious cardiovascular problems in healthy people.
American and British scientists looked at 14 clinical studies of more than 8,000 smokers.
They found the likelihood of developing serious heart problems was almost 72 percent higher in patients taking Chantix than those taking a placebo.
The Chantix drug-maker, Pfizer, says the study that appears in the Canadian Medical Association Journal is too limited to draw conclusions about the risks.
The FDA has already changed the labeling of Chantix with warnings about cardiovascular risk in people who already have heart disease after a previous study.