The U.S. Food and Drug Administration has issued an early about Pfizer Inc's anti-smoking drug, Chantix.

The U.S. Food and Drug Administration issued an early warning about Pfizer Inc's anti-smoking drug, Chantix. The FDA is analyzing reports of erratic and aggressive behavior and suicidal thoughts and behavior in patients taking the prescription drug, known generically as varenicline.

The FDA has started alerting the public earlier about a review.

Pfizer, the world's biggest pharmaceutical company, reported revenue of $241 million for Chantix in the third quarter of 2007. That is significant, but still not one of its major drugs.