U.S. regulators have warned that Pfizer's anti-smoking drug, Chantix, appears increasingly likely to be linked to serious psychiatric behavior. The FDA called for stronger label warnings.
After analyzing reports of suicidal thoughts and behavior, the FDA said the drug is effective but that patients should talk to their doctors about this new safety information.
The drug has been prescribed to about 4 million people in the U.S. since in 2006.