Tuesday, July 05, 2011

Meta-Analysis: Chantix Causes One Heart Attack for Every Three Patients It Helps Quit Smoking; Anti-Smoking Groups: Keep Chantix, Ban E-Cigs

A new meta-analysis published yesterday in the Canadian Medical Association Journal reports that the smoking cessation drug Chantix is associated with a 70% increase in serious adverse cardiovascular events, such as heart attacks, compared to placebo (see: Singh S, Loke YK, Spangler JG, Furberg CD. Risk of serious adverse cardiovascular events associated with varenicline: a systematic review and meta-analysis. Canadian Medical Association Journal 2011. DOI:10.1503/cmaj.110218).

The meta-analysis "analyzed data from 14 doubleblind randomized controlled trials involving 8216 participants. The trials ranged in duration from 7 to 52 weeks." The major finding was that "Varenicline was associated with a significantly increased risk of serious adverse cardiovascular events compared with placebo (1.06% [52/4908] in varenicline group v. 0.82% [27/3308] in placebo group; Peto odds ratio [OR] 1.72, 95% confidence interval [CI] 1.09–2.71."

The authors further estimated the effects of treating a population with Chantix in terms of the number of adverse cardiovascular events that would occur compared to the number of smokers who would quit smoking because of the use of Chantix. The results were as follows:

"Varenicline increases the chances of a successful quit attempt by twofold compared with unassisted smoking cessation. However, at the population level, most smokers quit unassisted. The number needed to treat with varenicline for one additional person to successfully quit smoking is estimated to be 10 (95% CI 8–13). Assuming a baseline risk of serious adverse cardiovascular events of 5.57% per year (among smokers with stable cardiovascular disease), the number needed to harm (the number needed to cause one additional serious cardiovascular event) with varenicline is estimated to be 28 (95% CI 13 to 213) per year. The risk of additional serious adverse events associated with varenicline use includes the potential for serious neuropsychiatric symptoms such as depressed mood, agitation and suicidal thoughts."

Thus, for every 30 patients treated with Chantix, this article predicts that three people will quit smoking successfully due to the Chantix but that one person will have a serious cardiovascular event like a heart attack. In addition, an unknown number may experience severe neuropsychiatric effects such as suicidal ideation.

Given these tradeoffs, as well as the fact that there are other smoking cessation medications available and the overall long-term success rate with Chantix is dismal, it hardly seems justified to recommend that Chantix remain a mainstay of a national smoking cessation strategy on a population level.

The Rest of the Story

The public health impact of these findings is substantial. According to one of the study authors, as quoted in MedPage Today: "'In absolute terms, it is a small difference,' first author Sonal Singh, MD, of Johns Hopkins, told MedPage Today. 'However, when you consider the difference from a population perspective, you get a very different picture. It is estimated that 7 million people in the U.S. were using Chantix last year. If you apply our results to the total number of users, I estimate that there were 62,500 cardiac events that were linked to use of Chantix. That is not a small number, by any standards.'"

So in addition to the more than 200 suicides that have been linked to Chantix, Singh is now estimating that Chantix causes 62,500 serious cardiac events (e.g., heart attacks) per year. This is all in the name of helping one person quit smoking out of every 30 who are treated. While I suppose it is possible that the benefits of Chantix still outweigh the risks, it is difficult for me to see how, given these numbers. It is clear that in the short-term, the benefits of reducing cardiac risk due to quitting smoking is overshadowed by the increased risk of severe adverse cardiovascular events.

In contrast to the 62,500 serious cardiac events attributable to Chantix each year, the use of electronic cigarettes to quit smoking has been associated with zero serious adverse events.
Nevertheless, the official policy recommendation of each of the following anti-smoking organizations is that Chantix should remain on the market while electronic cigarettes should be taken off the market until proven "safe and effective":
  • The Campaign for Tobacco-Free Kids;
  • The American Cancer Society;
  • The American Heart Association;
  • The American Lung Association;
  • Action on Smoking and Health;
  • The American Academy of Pediatrics; and
  • The American Legacy Foundation.
The glaring inconsistency in the policies of these anti-smoking groups is difficult to fathom, unless one also considers one other thing that each of these groups has in common:
  • All have or have had financial associations with Pfizer, the manufacturer of Chantix.

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