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UCSF study: cardiovascular safety concerns over Varenicline, a smoking-cessation drug, misleading

Varenicline ( Chantix, Champix ), a smoking cessation medication, has been under a cloud of suspicion ever since the Canadian Medical Association Journal ( CMAJ ) published a study July 2011 reporting risk of serious adverse cardiovascular events associated with the agent.
UCSF researchers, however, question the way the previous study was conducted, and their new analysis reaches a very different conclusion.

The researchers found no clinically or statistically significant increase in serious adverse cardiovascular events associated with using Varenicline. The findings from 22 trials with more than 9,200 participants have indicated a difference in risk of only 0.27% between those on Varenicline versus placebo.

Judith Prochaska and Joan F. Hilton, at UCSF ( University of California San Francisco ), conducted the new study, which, like the prior one, used meta-analytic statistical techniques to combine results from different trials of Varenicline with tobacco users. The UCSF and prior analysis, however, differed in several fundamental ways.

The previous study, led by Sonal Singh, at Johns Hopkins University, looked at a sample size of 8,216 patients in 14 trials and ¬¬¬reported a 72% ( relative ) increase in risk of heart attack or other serious heart problems.

The UCSF analysis included 22 double-blind, randomized controlled trials with 9,232 participants. More than half of the studies included participants with active or past history of cardiovascular disease. Eight trials had no events. The UCSF study found a 0.27% ( absolute ) risk difference, which it determined was neither clinically nor statistically significant.
Researchers identified 8 separate trials with nearly 1,600 tobacco users randomized to Varenicline or placebo that did not have a single serious cardiovascular event. The Singh analysis excluded these trials.

UCSF researchers say Varenicline lasts in the body about 7 days after a person stops using the medication. The new analysis examined events occurring during the drug treatment window or within 30 days after a patient stopped using the drug, rather than the entire trial period, which in many cases was a year in Singh’s study.

Singh’s study found that 1.06% of those who took Varenicline had serious heart-related complications, compared to 0.82% of the placebo group. Although the simple absolute difference was only 0.24%, similar to the UCSF study finding based on meta-analytic methods, Singh’s paper reported the weighted, relative difference, which was 72%.

Cardiovascular disease is the leading cause of death among smokers. Tobacco use also increases a person’s risk of stroke, cancer and lung disease. ( Xagena )
Source: University of California San Francisco, 2012