Pfizer's drug, Chantix, has already been linked to psychiatric side effects, but now has been found to increase the risk of heart attack in people with a history of heart disease. The risk in the placebo group was 0.9% and in the group on Chantix the risk was 200% higher with a percentage of 2.0. 2.3% needed coronary bypass procedures compared to 0.9% in the control group.
It appears that smokers are sufficiently desperate that they are often willing to take the risks of these problems to get help in quitting smoking.
