Rockville, MD - The Food and Drug Administration (FDA) announced yesterday that it has approved varenicline (Chantix, Pfizer), an oral nicotine-receptor blocker, to help cigarette smokers quit smoking. The FDA approved the drug under its priority-review mechanism, cutting months off the review time, because the agency deemed the drug and its approval as having a significant potential benefit to public health.

Varenicline is a nicotine-receptor partial agonist with effects on nicotine addiction. The drug works by partially blocking the alpha4-beta2 nicotinic receptor in the brain. When nicotine attaches to this receptor, it triggers an increase in dopamine, but by blocking nicotine from attaching, varenicline prevents the release of dopamine and the pleasurable sensation associated with smoking. The drug also has a partial activation effect on nicotine receptors that helps to curb withdrawal symptoms.

"Cigarette smoking is a very difficult habit to break, due in large part to nicotine dependence or addiction," commented Dr Steven Galson, director of the Center for Drug Evaluation and Research, in a press release issued by the FDA. "Chantix therapy has proven to be effective in smokers motivated to quit and will provide another tool for physicians to use for the millions of smokers who want to quit."

Data presented at the American Heart Association (AHA) 2005 scientific sessions in Dallas, TX, previously reported by heartwire, showed that smokers treated with varenicline for 12 weeks were significantly more likely to get off and stay off cigarettes for up to a year than those who received bupropion (Zyban, GlaxoSmithKline), a currently used antismoking drug, or those who received placebo. Varenicline showed "robust and superior efficacy" out to one year and was safe and well tolerated, Dr Serena Tonstad (Ulleval University Hospital, Oslo, Norway) said when presenting the results of three studies last year.

The FDA approval of varenicline was based on the results of six clinical trials, including the studies by Tonstad and colleagues, involving more than 3659 chronic cigarette smokers. One concern raised when the data were presented at the AHA last year was that many smokers relapsed after about a year. At the time, Dr Timothy Gardner (Christiana Care Health Services, Wilmington, DE) said the absolute numbers of participants who benefited from varenicline "were perhaps a little disappointing." Although the drug appeared to be superior to bupropion, the studies suggested that it may help keep less than half of smokers off cigarettes for up to 12 weeks and less than one quarter for 12 months, he said.

The approved treatment course for varenicline is 12 weeks. Patients who successfully quit smoking during treatment may continue with an additional 12 weeks of varenicline to further increase the chances of long-term smoking cessation. The most common side effects of varenicline observed in clinical trials were nausea, headache, vomiting, flatulence, insomnia, abnormal dreams, and a change in taste perception.