Pfizer Inc.'s Chantix, a stop-smoking drug whose active ingredient is varenicline, has received approval from the U.S. Food and Drug Administration (FDA), the Associated Press reported May 11.

The drug, which both blocks nicotine receptors in the brain and prevents withdrawal, is slated to go on sale later this year. Previous research found that more than 20 percent of users were able to quit smoking for a year or longer.

"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 Steven Schroeder, professor of medicine at the University of California at San Francisco.

The twice-daily pill, taken over 12 weeks, is the only stop-smoking drug other than the antidepressant bupropion (Zyban) that does not itself contain nicotine.

Thomas Glynn, director of cancer science at the American Cancer Society, said that while varenicline is "not going to be a revolution, it's going to be a substantial step forward."

Pfizer hopes to sell $1 billion worth of Chantix annually.