Pfizer stop-smoking pill raises heart risk: FDA

A man smokes a cigarette on World No Tobacco Day in Kathmandu May 31, 2011.

WASHINGTON (Reuters) - Pfizer's drug to help smokers quit, which has already been linked to psychiatric side effects, can lead to a small increase in heart problems in those who have cardiovascular disease, U.S. health regulators said on Thursday.

The Food and Drug Administration is changing the Chantix label to identify the increased heart risk after reviewing the results of a clinical trial.

An independent randomized trial of 700 smokers with cardiovascular disease who were treated with Chantix or a placebo showed that the Pfizer drug was effective in helping patients quit smoking for as long as one year.

However, patients who took the pill were also slightly more likely to have a heart attack or other adverse cardiovascular event compared with patients who received a placebo.

In the study cited by the FDA, 2 percent of patients taking Chantix had non-fatal heart attacks compared with 0.9 percent in the placebo group, while 2.3 percent of Chantix patients needed artery-clearing procedures versus 0.9 percent on placebo.

Many smokers who try to quit do so to prevent the risk of heart attacks, which may now be associated with Chantix.

"The known benefits of Chantix should be weighed against its potential risks when deciding to use the drug in smokers with cardiovascular disease," the FDA said in a statement.

The FDA said it is also requiring Pfizer to evaluate the cardiovascular safety of Chantix by conducting a large, combined analysis of randomized, placebo-controlled trials.

Pfizer said in a statement that it would be discussing details of such an analysis as well as the product's label with the FDA.

The company said that in a Chantix clinical trial of smokers with certain types of heart disease reports of adverse cardiovascular problems were low.

Pfizer's non-nicotine pill has already come under fire for psychiatric side effects and prompted the FDA to issue a restrictive "black box" warning on the drug's label.

Investors had high hopes for the drug -- called Champix in Europe -- when Pfizer first launched the smoking-cessation aid in 2006, but reports of psychiatric side effects have hampered strong sales growth.

Annual sales are now about $800 million, making the pill a moderate-sized product for the world's biggest drug maker.

Chantix has been associated with agitation, depression and suicidal thoughts, and, in clinical trials, was linked with nightmares. Psychiatric symptoms have occurred in people without a history of mental illness and have worsened in people who already had mental illness.

Pfizer shares closed up 5 cents at $20.25 on the New York Stock Exchange.

(Reporting by Anna Yukhananov; additional reporting by Bill Berkrot and Ransdell Pierson in New York; editing by Dave Zimmerman, Bernard Orr)