Wednesday, 6 July 2011

Pfizer anti-smoking drug in trouble over cardiovascular risks

WORLD (InPharm) Pfizer has been drawn into a war of words over its quit smoking pill - smoking cessation drug, they call it - Champix after a review of existing data suggested it was associated with increased risk of cardiovascular problems. The meta-analysis, published in the Canadian Medical Association Journal, analysed data from 14 trials involving Champix (varenicline, known at Chantix in the US) in more than 8,000 patients. The report’s authors, Singh et al, concluded that there were “safety concerns about the potential for an increased risk of serious adverse cardiovascular events associated with the use of varenicline among tobacco users”. But Pfizer is standing by its drug’s benefit/risk profile. “Pfizer scientists and doctors continuously evaluate the benefits and risks of its medicines, including Chantix,” said Gail Cawkwell, the manufacturer’s vice president of medical affairs.

“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,” Cawkwell went on.
“The authors themselves acknowledge that the cardiovascular risk ‘estimates are imprecise owing to the low event rates’,” the company added in a statement.
The FDA, which approved Champix in 2006, has already said it “may be associated with a small, increased risk of certain cardiovascular adverse events in patients who have cardiovascular disease”.
The US regulator looked at a randomised trial of 700 smokers with cardiovascular disease, which found Champix helped patients quit and remain abstinent from smoking for up to one year.
Although cardiovascular adverse events were infrequent, some - including heart attack - were more frequent in the Champix arm than in patients treated with placebo.
Safety information to that effect is already on the Warnings and Precautions section of the drug’s labelling for doctors.
Singh et al searched MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews and websites of regulatory authorities and registries of clinical trials to find published and unpublished studies.
It selected double-blind randomised controlled trials of at least one week’s duration that reported on cardiovascular events (ischemia, arrhythmia, congestive heart failure, sudden death or cardiovascular-related death) as serious adverse events.
But Pfizer questioned the “appropriateness of the authors’ measure of cardiovascular risk, or composite endpoint, which combines events that do not share a common biological cause”.
It also queried “the manner in which cardiovascular events were counted and classified; and a small number of events, which forms the authors' conclusions”.

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