2005 AHA Scientific Sessions: Varenicline efficacy trial

A nicotinic acetylcholine receptor partial agonist is an effective smoking cessation aid, said Serena Tonstad, MD, PhD, professor of nutrition at the Ulleval University Hospital, Oslo, Norway.

The agent, varenicline, "was developed to treat nicotine addiction by attaching to the nicotinic acetylcholine receptor," said Dr Tonstad, who is also head physician in the department of preventive cardiology. "As an agonist, it stimulates the receptor to decrease craving and withdrawal; as an antagonist, it blocks the receptor to decrease the reinforcement associated with smoking."

In 2 identical, randomized, double-blind studies that involved 2,045 smokers, treatment with varenicline 1 mg twice daily was compared with bupropion 150 mg twice daily and placebo for 12 weeks, followed by a 40-week non-treatment observation period. Quit rates were determined by measures of carbon monoxide in expired breath.

In the first study (N=1,022), continuous abstinence rates from Week 9 to Week 52 were 22.1% for varenicline, 16.4% for bupropion, and 8.4% for placebo (P=.064 vs bupropion; P<.0001 vs placebo). Results from the second study (N=1,023) were similar: The continuous abstinence rates were 23.0%, 15.0%, and 10.3% for varenicline, bupropion, and placebo, respectively (P=.006 vs bupropion; P<.0001 vs placebo).

The benefit of 12 more weeks of varenicline treatment was examined in a separate open-label maintenance study of 1,206 subjects who remained smoke-free at the end of 12 weeks. Under the open-label conditions, the continuous abstinence rates (Weeks 13 to 24) were 70.6% for those receiving varenicline compared with 49.8% for those receiving placebo (P<.0001). For Weeks 13 to 52, the continuous abstinence rates were 44% for varenicline and 37% for placebo (P=.013).

Mild nausea was the most common side effect of varenicline; treatment discontinuations due to nausea were 2.3% to 2.6% in the short-term studies, 1.4% in the open-label phase, and 0.2% in the maintenance study.