The Food and Drug Administration on Tuesday said it has received reports of mood disorders and erratic behavior among patients taking Chantix. The drug won regulatory approval last year to aid adults trying to quit smoking and sales totaled $101 million.
FDA said it is still gathering information about the drug, but advised doctors to closely monitor patients taking Chantix for behavior changes. The agency said the changes have often been reported within days or weeks of people first taking the drug.
Pfizer said Tuesday it added information about the reports to the product's label, but stressed "there is no scientific evidence establishing a causal relationship between Chantix and these events."
Pfizer said in a statement there were no suicides in a 5,000-patient study of the drug.
FDA said it is investigating at least one incident of a patient who died while reportedly taking the drug.
Family members of Dallas musician Carter Albrecht recently said Chantix may have caused the rage that ultimately led to his death. Albrecht was shot in the head in September by his girlfriend's neighbor as he tried to kick down the man's door. An autopsy report showed Albrecht's blood alcohol was three times the legal limit.
FDA said it has asked Pfizer for information on additional cases that might be similar.
Regulators said it was unclear if Chantix was directly responsible for the behavior, since nicotine withdrawal often aggravates existing mental problems.
New York-based Pfizer also submitted reports to the FDA about drowsiness among Chantix patients that interfered with their ability to drive. Pfizer said clinical studies of the drug showed no significant difference in drowsiness between patients taking Chantix and those taking a dummy pill.