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Troubled anti-smoking drug linked to heart risks

smoker-260.jpgA controversial drug meant to help users stop smoking has now been linked to cardiovascular risks including heart attack and stroke.

Chantix (varenicline), which is made by New York-based Pfizer, was already under fire for possibly causing other disturbing side effects, including hostility and suicidal behaviour. The Institute for Safe Medication Practices, a non-profit group that monitors drug safety, has said that Chantix generates more reports of aggression, depression, and psychosis than any other drug on the market. And as of March 15, 2011, Chantix was the star in 1545 drug-injury lawsuits.

Now, clinical trials expert Curt Furberg of Wake Forest University School of Medicine in Winston-Salem, North Carolina and his colleagues report that the drug also boosts the risk of serious cardiovascular events. In a meta-analysis of 14 trials involving 8216 participants, Furberg and his colleagues found that the risk of cardiovascular events was 72% higher among those who take Chantix. The results were published yesterday in the Canadian Medical Association Journal.

How will regulators handle the new information? The US Food and Drug Administration (FDA) recently added a warning to what must already be a very crowded Chantix label, this time addressing the increased risk of cardiovascular events among smokers with cardiovascular disease.


Earlier this year, analysts for the Institute for Safe Medication Practices – including Furberg – found that Pfizer had misclassified hundreds of reports of suicide, suicide attempt, and psychosis as ‘expected adverse events’ rather than ‘serious adverse events’. As a result, the data was buried in an unsearchable report containing 26,000 events, most of them minor. But the FDA countered that the added data did not change its assessment of Chantix, which already bears a warning about possible psychiatric side effects, and noted that it had asked Pfizer to conduct a postmarketing safety study comparing Chantix to other anti-smoking drugs.

Update: FDA spokesman Jeff Ventura says that in 2008 the FDA told Pfizer to conduct a postmarketing clinical trial assessing the safety of Chantix among other smoking cessation aids. The trial is to be completed in August 2016, and the final study report is due April 2017. (Interestingly, that data will be arriving just in time for Pfizer’s patent on Chantix to expire in 2018.)

But Sonal Singh of Johns Hopkins, first author on the new Chantix study, says he’s not holding his breath for the data because the trial is likely to be too small to reveal a significant safety risk. He points out a recent study which failed to find any cardiovascular risks of taking Chantix among those who already have heart disease. The problem, he says, is that the study was simply underpowered.

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