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Pfizer questions study that faults Chantix's safety

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Pfizer Inc. on Monday defended the safety record of its smoking-cessation drug Chantix after results of a Canadian analysis were released tying the treatment to an increased risk of heart disease among those who had never before reported symptoms.

Pfizer said it questioned the analysis led by Sonal Singh of Johns Hopkins University School of Medicine and published by the Canadian Medical Association Journal.

"The currently available safety data on Chantix, including a pooled analysis of clinical data in 7,375 people trying to quit smoking, do not support an increased cardiovascular risk associated with Chantix," Pfizer said in a statement.

The company added that the "authors themselves acknowledge that the cardiovascular risk 'estimates are imprecise owing to the low event rates.' "

But Singh, in a statement, questioned whether Chantix - whose active ingredient was developed at Pfizer research sites in Groton and New London - should be on the market.

"People want to quit smoking to reduce the risk of cardiovascular disease," he said, "but in this case they are taking a drug that increases the risk for the very problems they are trying to avoid."

While the journal article cited a 72 percent increase in reported serious cardiovascular events for those on Chantix, Pfizer said the actual rate of heart problems reported increased only from 0.82 percent for those on placebo to 1.06 percent for those taking the smoking-cessation drug.

"Pfizer scientists and doctors continuously evaluate the benefits and risks of its medicines, including Chantix," said Dr. Gail Cawkwell, vice president of medical affairs for Pfizer, in a statement. "The currently available safety data on Chantix ... do not support an increased cardiovascular risk associated with Chantix."

Pfizer said it is discussing with the U.S. Food and Drug Administration the possibility of conducting its own analysis of previous clinical-trial data to re-evaluate Chantix's safety profile.

"This meta-analysis will address a number of limitations in the Singh analysis," the company said. "Pfizer expects that it will be based on a more reliable composite endpoint to measure cardiovascular risk, as well as a validated process to classify, or adjudicate, cardiovascular events that are part of the composite endpoint."

New questions about Chantix follow reports last month that France had removed the smoking-cessation pill from a list of state-approved remedies. The removal occurred after widespread concerns were expressed about the drug's most-reported side effects, which include violent rages and suicidal thoughts.

At the time, the FDA said it didn't have any new safety concerns about Chantix. But the agency later in the month issued a safety notice about Chantix, saying a study of 700 people with a history of cardiovascular disease showed an increased risk of problems for those taking Pfizer's smoking-cessation pill.

The new journal analysis looked at only people without a history of heart problems.

Chantix contributed $755 million in worldwide sales to Pfizer's bottom line last year, and it has been prescribed for more than 13 million patients in 99 countries.

l.howard@theday.com

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