Doctors say a pill first developed in Bulgaria during the days of the Iron Curtain may be a cheap and easy way of getting millions of smokers to give up the habit.

The first major study of the drug called cytisine appears in Thursday's issue of the New England Journal of Medicine.

Cytisine is derived from laburnum seeds, which researchers call a natural nicotine substitute. A study carried out with hundreds of smokers in Poland shows those given cytisine were more than three times as successful in quitting cigarettes than those given placebos.

Cytisine has been available under various brand names throughout Eastern Europe for decades. Experts say it has a much higher success rate and costs just a fraction of better-known cigarette substitutes such as gums and nicotine patches.

But the experts say it is not likely to become available in Western Europe or the United States soon because of government regulations.

Medical officials say 95 percent of smokers who try to quit without drugs or other help fail within months.

Cigarette smoking kills millions around the world every year. Doctors say it is the number one cause of preventable deaths.