Pfizer Adds Strong Warning to Anti-Smoking Drug CHANTIX

Government regulators said Friday the connection between Pfizer's anti-smoking drug Chantix and serious psychiatric problems is "increasingly likely."

The Food and Drug Administration began in November investigating reports of depression, agitation and suicidal behavior in patients taking the popular twice-daily pill.

The agency's announcement comes two weeks after Pfizer added stronger warnings to the drug. In doing so, the company stressed that a direct link between Chantix and the reported psychiatric problems has not been established, but could not be ruled out.