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Varenicline (Chantix, Pfizer), the first in a class of quit-smoking medications that recently entered the market, has tobacco-cessation experts abuzz with excitement.
"This is a very encouraging new option for physicians who want to successfully treat tobacco dependence and for patients who've had trouble quitting in the past," says Michael Fiore, MD, director of the Center for Tobacco Research and Intervention at University of Wisconsin Medical School in Madison. "It's not going to automatically turn a smoker into a nonsmoker, of course. But for patients who are motivated to quit, varenicline is an important addition to the armamentarium."
Varenicline works differently from nicotine-replacement therapies, such as patches and gum, and the well-studied antidepressant bupropion (Zyban, GlaxoSmithKline). It is the first in a class of drugs known as selective nicotinic acetylcholine receptor partial agonists.
"Essentially, this medication competes with nicotine at the receptor site in the brain," says David Gonzales, PhD, researcher and co-director of the Oregon Health and Science University Smoking Cessation Center in Portland. Once varenicline attaches to that brain receptor, there's less room for any circulating nicotine to bind.
"The effect is that smokers taking varenicline get less of that pleasurable rush from nicotine when they smoke, so it's less rewarding," Gonzales explains. "And when they do stop tobacco, they feel fewer cravings and withdrawal symptoms on the medication."
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THE DATA
The effectiveness of varenicline—which was approved by the U.S. Food and Drug Administration in May—was demonstrated in six clinical trials that included >3,600 chronic smokers treated with the drug. Prior to treatment, the smokers averaged a pack of cigarettes per day for approximately 25 years.
Five of the studies were randomized, controlled trials that showed varenicline to be superior to placebo in helping people quit over a period of several weeks. And in two of the trials, patients taking varenicline also had greater long-term quitting success than patients given the popular quit-smoking drug bupropion. Some of these phase III trials were published recently in JAMA1–3 and Archives of Internal Medicine.4,5
The most common side effect for varenicline users was nausea, but few patients discontinued using the medication because of it.
"Our results suggest that nausea is dose-related and that titration [during the first week of treatment] reduced the incidence," notes researcher Cheryl Oncken, MD, MPH, of the University of Connecticut Health Center in Farmington.
Varenicline is generally started a week before the patient's chosen quit date and continued for a 12-week course after smoking has stopped, according to Pfizer. In some cases, physicians may recommend an additional 12 weeks' maintenance regimen of the medication.
The cost for 168 0.5 mg or 1 mg tablets is about $300.6 Either dosage, taken twice daily, costs $3.57 per day.
Tobacco cessation experts also emphasize that, in addition to writing a prescription for varenicline or any quit-smoking aid, clinicians also should urge motivated patients to call the National Network of Tobacco Cessation Quitlines (800-QUIT-NOW) before their quit date. This network links patients to a trained tobacco-cessation counselor either in their area or at the National Cancer Institute (DOC News, April 2005).
"This counseling and support piece really increases the odds of
success, without question," Fiore says. 
References
2. Jorenby DE, Hays JT, Rigotti NA, et al.: Efficacy of varenicline,
an alpha4beta2 nicotinic acetylcholine receptor partial agonist, vs. placebo
or sustained-release bupropion for smoking cessation: A randomized controlled
trial. JAMA 296:56–63, 2006.
3. Tonstad S, Tonnesen P, Hajek P, et al.: Effect of maintenance
therapy with varenicline on smoking cessation: A randomized controlled trial.
JAMA 296:64–71, 2006.
4. Nides M, Oncken C, Gonzales D, et al.: Smoking cessation with
varenicline, a selective alpha4beta2 nicotinic receptor partial agonist:
Results from a 7-week, randomized, placebo- and bupropion-controlled trial
with 1-year follow-up. Arch Intern Med 166: 1561–1568, 2006.
5. Oncken C, Gonzales D, Nides M, et al.: Efficacy and safety of the
novel selective nicotinic acetylcholine receptor partial agonist, varenicline,
for smoking cessation. Arch Intern Med 166: 1571–1577, 2006.
6. www.drugstore.com, accessed September 22, 2006.
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