About 5 million people globally die prematurely from smoking each year, the study authors noted.
The study, published in the Sept. 29 issue of the New England Journal of Medicine, was largely paid for by Britain's publicly funded National Prevention Research Initiative.
For the study, West's team randomly assigned 740 smokers to cytisine or a placebo for 25 days. In addition, the participants received minimal counseling to help them quit. More than 80 percent of participants had already tried to quit.
After one year, 8.4 percent of those who had taken cytisine were still not smoking, compared with 2.4 percent of those who received the placebo, the researchers found.
Adverse side effects occurred more often in those receiving cytisine and included stomach ache, dry mouth, difficulty breathing and nausea. But, these were generally mild and not long lasting, the authors noted.
Commenting on the study, Dr. Michael C. Fiore, a professor of medicine and director of the Center for Tobacco Research and Intervention at the University of Wisconsin School of Medicine and Public Health in Madison, said that "the findings are encouraging and promising, but need to be replicated."
Around the world there are about one billion smokers, Fiore said. "Many of them want to quit, but don't have access to the counseling we know would help, and many of the medicines are too expensive for them to purchase," he said.
"If there is a medication that is safe, effective and inexpensive, it would be an important advance," he added. However, the results of this study need to be replicated in other groups to ensure that it is both safe and effective before cytisine can be considered such a drug, he said.
Another expert, Dr. Steven Schroeder, director of the Smoking Cessation Leadership Center at the University of California, San Francisco, added that "if cytisine comes on the market in the U.S.
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