Smoking tobacco killed 100 million people over the course of the 20th century. It is a leading cause of cancer, heart disease and other ailments. And it is on pace to kill one billion more this century if current trends continue. Yet, quitting smoking is hard to do for a variety of physiological and psychological reasons. New research indicates, however, that a novel drug--based on an older plant cure--aids heavy smokers in their quest to quit.

Cheryl Oncken, M.D., of the University of Connecticut and her colleagues put together two randomized, double-blind studies of a new drug--varenicline tartrate--with funding from Pfizer. The compound works by blocking nicotine from receptors by binding to them itself and triggering lesser physiological effects, which may help smokers resist the temptation to light up. This is exactly what the first study of 626 smokers revealed: those given the highest dose of varenicline quit at nearly three times the rate of those given only a placebo--48 percent and 17 percent respectively. The drug also outperformed an antidepressant, bupropion hydrochloride, sometimes used as a quitting aid. And one year after treatment, 14 percent of those smokers using varenicline remained free of cigarettes, compared to just 6 percent of the bupropion-treated and less than 5 percent of those given a placebo.

Varenicline did show some side effects, including nausea, but the second study of 647 heavy smokers revealed that spacing out the dose of the drug over the course of the day could limit that impact while maintaining high quitting rates. "Varenicline tartrate is efficacious for smoking cessation," the researchers conclude in a paper presenting the research in the current issue of Archives of Internal Medicine.

Unfortunately, this quitting aid could have been discovered long ago: the leaves of Cytisus laburnum, or the golden rain tree, were used as a tobacco substitute by soldiers in World War II. They contain cytisine, which, like nicotine, is an insecticide and upon which varenicline is based. Research in eastern Europe, Russia and Germany over the past 40 years seemed to show that cytisine was effective in helping smokers stop smoking but remained largely unnoticed by English-language researchers. "How many other effective drugs are there for which efficacy remained unnoticed because existing trials were not published in English?" asks Jean-Francois Etter of the University of Geneva in an accompanying review. Regardless, "all these advances will deliver real aid to curbing smoking," notes Bankole Johnson, M.D., of the University of Virginia in an accompanying commentary. "Now, a smoker who wants help to quit no longer has a legitimate excuse to delay seeking treatment."