An anti-smoking drug sold by Pfizer Inc will carry more prominent warnings that patients be monitored for unusual activity including agitation, depression and suicidal behavior, the company said on Friday.
The world's largest drugmaker said it worked with the U.S. Food and Drug Administration to update an earlier label change enacted last year for its drug Chantix.
The new label offers a similar recommendation to monitor patients, but the language is more prominently located to better get the attention of doctors, Pfizer officials said.
"Basically there was an evolution of thinking of where it would be best to place (the advice) on the label," Pfizer Vice President for Medical Affairs Ponni Subbiah said in an interview.
New York-based Pfizer said no causal relationship has been established between the drug and the behaviors, but in some cases, an association could not be ruled out.
The drug has been prescribed to 4 million people in the United States since approval in 2006, according to Pfizer.
The revised section is not a "black box," a warning reserved for what the FDA deems the most dangerous potential adverse events.
It directs doctors to observe patients on Chantix for "serious neuropsychiatric symptoms, including changes in behavior, agitation, depressed mood, suicidal ideation and suicidal behavior," according to Pfizer.
In November, the FDA issued an early warning after receiving reports of suicidal thoughts and behavior, and at least one death, potentially linked to the medication.
The FDA has been analyzing reports of erratic and aggressive behavior, and suicidal thoughts and behavior in patients taking the prescription drug, known generically as varenicline.
Pfizer said reports may be complicated by patients with pre-existing psychiatric illness and by symptoms of nicotine withdrawal.
The November FDA assessment revealed "that many of the cases reflect new-onset of depressed mood, suicidal ideation (thoughts) and changes in emotion and behavior within days to weeks" of starting treatment.
Pfizer reported third-quarter sales of $241 million in the for Chantix, up from $33 million a year earlier. Although not huge by Pfizer standards, some analysts are hoping the drug can help bolster profits as other major drugs face generic competition.
Typically only a fraction of adverse events are reported to the FDA.