Smokers taking a course of cytisine are twice as likely to kick the habit, researchers found as the UK prepares to introduce the plant-based drug this month.

Scientists found that the treatment was twice as effective as a placebo — and marginally better than nicotine substitutes — in research published earlier this week in the medical journal Addiction.

The findings come as the drug becomes available in the UK almost five years after its regulatory clearance. Consilient Health, an Irish drugmaker, plans to start selling it Jan. 22.

Cytisine has been used in eastern Europe since the 1960s to help people give up smoking under brand names such as Tabex. It’s also available in Canada, where it’s called Cravv, but not in most of the world.

A 25-day course of pills will cost the National Health Service £115 ($145.2), according to Consilient.

The drug hasn’t been a global success because clinical trials needed to license it in many countries may be too expensive considering it’s an aging generic that won’t command high prices, scientists wrote in an Addiction editorial advocating broader access in July 2016.

Smoking costs the UK economy around £17 billion a year, according to research by charity Action on Smoking and Health, placing a burden on the NHS and social care.

“Smoking is considered the main cause of preventable death,” Omar De Santi, a toxicology doctor at the Centro Nacional de Intoxicaciones in Buenos Aires and the research’s lead author, said in a statement. “Cytisine has the potential to be one of the big answers to that problem.”

The research was a so-called meta analysis that looked at 12 available studies on cytisine. It found no major safety concerns.

Consilient says cytisine’s active ingredient is a plant alkaloid with a structure similar to nicotine that alleviates withdrawal symptoms while also reducing the pleasure derived from smoking.