Despite smoke-free laws enacted during the past decade, smoking rates in the United States have remained relatively constant. According to the Centers for Disease Control and Prevention, approximately 21 percent of American adults smoke, and nearly 20 percent of high school students do so.
Cigarette smoking accounts for one of every five U.S. deaths each year, making it the nation’s leading preventable cause of death. Interventions that favorably impact this compelling statistic are hard to find. The relapse rate among smokers who try to quit – no matter what modality they use – is quite high, and most smokers make more than one attempt before they finally succeed in quitting. A March 2002 American Family Physician review revealed that, while 70 percent of smokers express a desire to quit, only 7.9 percent are able to do so without help.
In 2006, varenicline (Chantix) was approved for marketing in the U.S. following a priority review by the Food and Drug Administration. It has since become one of the most widely prescribed – and most effective – medications for smoking cessation. Unfortunately, drugs that receive priority review have limited safety data upon approval, and many do not receive sufficient ongoing scrutiny once they are in general use.
How Does Chantix Work?
Your nervous system is “wired” to respond to tobacco by virtue of nicotinic receptors located in your brain, muscles, and other tissues. Unlike many medications used to help patients stop smoking, Chantix directly stimulates some of the same nicotinic receptors that are triggered when you smoke a cigarette.
Essentially, Chantix acts as a proxy for the nicotine you would receive from smoking. By binding to nicotinic receptors in your nervous system, the drug reduces nicotine cravings, which allows you to reduce cigarette use and alter the behaviors that contribute to your smoking habit.
Meta-Analysis Reveals Chantix Slightly Increases Cardiovascular Risk
Nicotinic receptors regulate a number of physiologic activities in your body, including your heart rate and blood pressure. Stimulation of nicotinic receptors – by nicotine or Chantix – elevates your blood pressure and your heart rate and promotes irritability in your heart’s conduction system.
In someone whose risk for cardiovascular disease is already increased (as it is in all smokers), stimulation of nicotinic receptors could precipitate a heart attack, stroke, or deadly arrhythmia, or it could stress an already overtaxed heart and contribute to heart failure. Furthermore, nicotine (and possibly Chantix) exerts a “prothrombotic” effect in your bloodstream, which enhances your blood’s tendency to clot and further heightens your chances for a cardiovascular event.
In the July 2011 Canadian Medical Association Journal, a meta-analysis of 14 clinical trials involving over 8,000 subjects revealed a “statistically significant” increase in the risk for serious cardiovascular events among tobacco users who took Chantix. However, statistics generated in clinical trials don’t always translate into clinical reality, particularly when the benefits of a treatment modality are themselves significant.
In the CMAJ analysis, 1.06 percent of Chantix users experienced a “serious adverse cardiovascular event,” compared to 0.82 percent of the subjects who took placebos. While this difference becomes statistically significant when thousands of patients are considered, your individual odds of having a Chantix-related heart attack, stroke, or other adverse event hover around 1 in 100.
The rate of abstinence among Chantix users – the “success rate” for smokers who quit – varies from 20 to 47 percent, depending on the length of the study and the duration of post-study follow-up. It is worth noting that smokers with coronary artery disease who quit smoking reduce their risk of death from all causes – cardiovascular disease, lung disease, cancer, etc. – by 36 percent.
“There Are Three Kinds of Lies…”
Statistical analyses of clinical trials are noteworthy for their “spin-ability.” For example, when the general public is informed of a “30 percent higher risk of heart attack” associated with a given treatment, they may not necessarily be told that their individual risk for such an event is still quite small. On the other hand, significant risks are often downplayed to expedite a drug’s approval and enhance its eventual marketability.
Certainly, statistically relevant findings should prompt warnings, surveillance, and further clinical trials, but the risks associated with a treatment modality must be weighed against its clinical (i.e., real-life) benefits.
Smoking remains a serious public health issue. Chantix has proven to be a valuable asset in smoking cessation programs, with abstinence rates that surpass many other therapeutic interventions. While its use should be approached with caution – particularly among smokers with known coronary artery disease – it should not be discarded as an option for any smoker who earnestly wishes to quit.
Sources
- Centers for Disease Control and Prevention: FastStats – Smoking.
- R Mallin. Smoking cessation: integration of behavioral and drug therapies. Am Fam Phys. 2002;65(6):1107-1115.
- S Singh, et al. Risk of serious adverse cardiovascular events associated with varenicline: a systematic review and meta-analysis. CMAJ. July 4, 2011.
- NA Rigotti, et al. Efficacy and safety of varenicline for smoking cessation in patients with cardiovascular disease. Circulation. 2010;121(2):221-229.
Stephen Allen Christensen - Dr. Steve Christensen's writing has appeared in magazines, professional journals, poetry anthologies, and children's books since 1976.
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