Varenicline for smoking cessation: Is it a heartbreaker?
See related research article by Singh and colleagues at http://www.cmaj.ca/lookup/doi/10.1503/cmaj.110218.
In this week’s CMAJ, Singh and colleagues1 cardiovascular disease. A considerable evidence Competing interests:
present a meta-analysis assessing the risk of
base supported by multiple randomized con-
J. Taylor Hays has receivedgrant funding from Pfizer to
serious adverse cardiovascular events asso-
trolled clinical trials and meta-analyses shows
ciated with the use of varenicline for smoking
that varenicline consistently more than doubles
cessation. The paper raises additional questions
the chances of long-term abstinence from to -
bacco.5,8,9 Thus, varenicline should be an important
scrutiny by the US Food and Drug Administra-
tool for reducing cardiovascular events among
tion for neuropsychiatric safety concerns,2 and
patients who smoke. How then are we to interpret
Correspondence to:
within the past month, the drug has been the focus
and apply the results of the meta -analysis pro-
of another warning regarding an association
vided by Singh and colleagues1 to our clinical
between it and serious adverse cardiovascular
practices? In this regard, there are several impor-
CMAJ 2011. DOI:10.1503
events.3 This new warning is based on observa-
/cmaj.110804
tions published in a randomized trial of vareni-
First, the main result of the meta-analysis, a
cline for the treatment of tobacco dependence
72% increased risk of serious cardiovascular
among participants with known cardiovascular
adverse events, must be tempered by the rarity of
disease.4 Certain serious adverse cardio vascular
these events among partipants in both treatment
events were seen more frequently among partici-
groups (1.06% among patients given varenicline
pants receiving varenicline than among those
and 0.82% among patients given a placebo) —
receiving a placebo, but the differences failed to
an absolute percent difference of only 0.24%.
reach statistical significance and events were
Second, as noted by Singh and colleagues, the
rate of participants lost to follow-up was greater
The concerns about the cardiovascular safety of
in the placebo arm than in the treatment arm in
varenicline raised by this new warning makes the
most of the studies included in the analysis. This
meta-analysis by Singh and colleagues1 timely and
introduces bias in determining serious, adverse,
important. Varenicline is efficacious for smoking
cardiovascular events that favours fewer events
cessation,5 but could this be one more case in
counted among participants given a placebo.
which the treatment is worse than the condition
Third, cardiac events were adjudicated in only
being treated? A measured view of the evidence of
a single study.4 As mentioned earlier, in that
the harms of smoking compared with the potential
study, no significant differences were seen in the
harms of varenicline treatment suggests otherwise.
incidence of cardiovascular events or in mortality
between people receiving varenicline and those
British male doctors, Doll and colleagues showed
that smoking kills more than half of persistent
Finally, although the point estimates for the
smokers.6 In the similarly influential Nurses’
number needed to treat (10) and the number needed
Health Study (a prospective cohort study), 104 000US women were followed for 20 years, and the
relative risk of mortality from coronary heart dis-ease among women who smoked was four to five
• When used as a treatment for tobacco dependence, varenicline may be
times the risk seen among women who had never
associated with an increase in adverse cardiovascular events.
smoked.7 This study also showed that quitting
The absolute increase in the rate of serious cardiovascular events associated
smoking is associated with a rapid decline in risk
with varenicline versus placebo is less than 1% based on analysis of morethan 8200 participants involved in 13 randomized clinical trials.
of death due to coronary heart disease, with over60% of the full potential benefit occurring within
Smoking kills more than half of persistent smokers and reduces lifeexpectancy by up to 10 years, whereas smoking cessation rapidly
reduces the risk of future cardiovascular events.
Given such evidence, there is no doubt that
Varenicline should continue to be used with appropriate caution to limit
effective treatment for tobacco dependence will
adverse effects, while capitalizing on its benefits for smoking cessation.
reduce the risk of death and morbidity related to
to treat for harm (28) are similar, the degree of
that it is.5,8,9 Is varenicline risk free? Clearly it is
uncertainty for the number needed to treat for harm
not, as the meta-analysis presented by Singh and
(upper bound of 95% confidence interval [CI] 213)
colleagues shows.1 However, the risk for serious
is considerably greater than it is for the number
cardiovascular adverse events is low and is greatly
needed to treat (upper bound of 95% CI 13). These
outweighed by the benefits of diminishing the
results represent a significant degree of uncertainty
truly “heartbreaking” effects of smoking.
about the relative good or harm from varenicline,leaving the issue unsettled. As such, how should
References
the results of this meta-analysis guide future studies
Singh S, Loke YK, Spangler JG, et al. Risk of serious adverse car-
diovascular events associated with varenicline: a systematic reviewand meta-analysis. CMAJ 2011; July 4 [Epub ahead of print].
The best outcome from this analysis would be
US Food and Drug Administration. The smoking cessation aids
more rigorous and adequately powered studies
varenicline (marketed as Chantix) and bupropion (marketed asZyban and generics): suicidal ideation and behavior. FDA Drug
evaluating the safety of using varenicline among
Safety Newsletter 2009;2:1-4.
smokers who have known cardiovascular disease.
Rigotti NA, Pipe AL, Benowitz NL, et al. Efficacy and safety ofvarenicline for smoking cessation in patients with cardiovascular
The worst outcome would be for health care
disease: a randomized trial. Circulation 2010;121:221-9.
providers to abandon the use of varenicline,
US Food and Drug Administration. FDA Drug Safety Commu-nication: Chantix (varenicline) may increase the risk of certain
which has proven to be among the most effica-
cardiovascular adverse events in patients with cardiovascular
cious pharmacotherapies used for the treatment
disease. Available: www .fda .gov /drugs /drugsafety /ucm259161
Cahill K, Stead LF, Lancaster T. Nicotine receptor partial ago-
nists for smoking cessation. Cochrane Database Syst Rev 2011;
“carefully balance” the risks and benefits of
Doll R, Peto R, Boreham J, et al. Mortality in relation to smok-
varenicline.1 Although their results suggest that
ing: 50 years’ observations on male British doctors. BMJ 2004;
a measure of caution should be taken in pre-
Kenfield SA, Stampfer MJ, Rosner BA, et al. Smoking and
scribing varenicline for the treatment of tobacco
smoking cessation in relation to mortality in women. JAMA
dependence, the small absolute risk of cardio-
Eisenberg MJ, Filion KB, Yavin D, et al. Pharmacotherapies for
vascular events associated with taking vareni-
smoking cessation: a meta-analysis of randomized controlled tri-
cline is outweighed by the enormous benefit of
reducing cardiovascular morbidity and mortality
Treating tobacco use and dependence: 2008 update. Clinicalpractice guideline. Rockville (MD): US Department of Health
that can be achieved with successful abstinence
and Human Services. Public Health Service; 2008.
Is varenicline a safe drug? Multiple random-
Affiliation: J. Taylor Hays is with the Department of Medi-
ized clinical trials and meta-analyses indicate
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