The FDA has approved a stop-smoking drug by Pfizer that satisfies nicotine cravings and diminishes the satisfaction of smoking to prevent relapse, the agency reported.

The agency gave the drug, called Chantix (varenicline tartrate), a priority review, which means the agency had six months instead of 10 months to approve or deny the application.

Chantix targets sites in the brain that are affected by nicotine in two ways to help smokers quit: It provides some of the effects of nicotine to ease withdrawal symptoms and also blocks the effect of nicotine if smokers resume smoking, FDA officials said during a conference call with reporters.

Clinical trials show Chantix is more effective than GlaxoSmithKline's smoking cessation drug Zyban (bupropion HCl), according to the FDA. Pfizer conducted a total of six clinical trials with the drug. Results from the two trials that included Zyban show 44 percent of patients taking Chantix stopped smoking after taking the drug for eight weeks, compared to 30 percent of those taking Zyban and 17 percent of those on placebo.

Smokers who were able to quit by taking Chantix are more likely to stay smoke-free for one year if they take a second course of the drug, officials said.