WASHINGTON – A tablet shown to help more than one in five smokers quit on Thursday joined the limited number of effective stop-smoking drugs approved by federal regulators. When varenicline goes on sale later this year, it will become the first new prescription drug for smoking cessation approved by the Food and Drug Administration in nearly a decade and only the second stop-smoking drug that is nicotine-free, according to Pfizer Inc. The New York company plans to market the twice-daily tablet, intended for adults only, as Chantix. “It’s a welcome new addition. It’s like with cancer or heart disease or high blood pressure or diabetes: The more effective treatments you have, the better off patients are,” said Dr. Steven Schroeder, a professor of medicine at the University of California, San Francisco, who is active in smoking cessation efforts. 160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! AD Quality Auto 360p 720p 1080p Top articles1/5READ MOREBasketball roundup: Sierra Canyon, Birmingham set to face off in tournament quarterfinalsVarenicline works in two ways, by cutting the pleasure of smoking and reducing the withdrawal symptoms that lead smokers to light up over and over again. Most other stop-smoking drugs are various nicotine-replacement therapies, sold by prescription and over the counter in gum, patch, lozenge, nasal spray or inhaler form. In 1997, the FDA approved bupropion, an antidepressant already sold as Wellbutrin but rebranded as Zyban, an anti-smoking drug.