Chantix, a pill that can assist people who wish to stop smoking, appears to raise the risk of a heart attack or cardiac problem substantially, according to a new study.

The specific cardiac risks linked to the drug, which is also known as varenicline, are only now coming into focus. Last month, the Food and Drug Administration issued a warning that Chantix may slightly increase the risk of a heart attack or other heart problems among people who already have heart disease. The FDA based its findings on data that showed seven out of 353 people taking Chantix had a nonfatal heart attack compared with three out of 350 people who took a placebo.

But the new paper, published Tuesday in the Canadian Medical Assn. Journal, analyzes 14 previous randomized, double-blind trials on the drug. Based on this data, of more than 8,000 healthy people, those who took Chantix had a 72% increased risk of having a heart attack or arrhythmia. Serious cardiovascular events occurred among 61 of 4,908 people who took Chantix compared with 29 out of 3,308 taking a placebo.

The new data may give smokers who wish to quit, and their doctors, pause. Chantix clearly helps some smokers quit. According to the FDA, about 19% of people who take the drug are able to abstain from smoking for at least one year compared with 7% of people taking a placebo. But the medication already carries a warning because it can cause suicidal thoughts and behaviors in some people.


“I think our new research shifts the risk-benefit profile of varenicline,” the lead author of the study, Sonal Singh, of Johns Hopkins University School of Medicine, said in a news release. “People should be concerned. They don’t need Chantix to quit and this is another reason to consider avoiding Chantix altogether.”

People who take Chantix should check with their doctor if they experience any new symptoms, such as shortness of breath or chest pain, said FDA officials.

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