FDA keeps suicide warning on anti-smoking drug

A man smokes by the fountains in Trafalgar Square in London, on Wednesday, Oct. 15, 2014. (AP Photo/Kirsty Wigglesworth)

WASHINGTON -- The Food and Drug Administration is keeping a bold-letter warning on Pfizer's anti-smoking drug Chantix about suicidal behaviour and other psychiatric side effects, after reviewing company findings suggesting the drug does not increase those problems.

The twice-a-day tablet has carried the FDA's strongest warning label since 2009, following reports of suicidal tendencies and violent or bizarre behaviour among some patients.

The FDA on Monday outlined several updates to Chantix's labeling, including a new warning about its potential interaction with alcohol. Some patients have reported unusual or aggressive behaviour when drinking while on Chantix.

The updated labeling also includes information from several studies and analyses conducted by Pfizer that found no difference in psychiatric problems between people taking Chantix and other stop-smoking treatments. But the FDA said Pfizer's research did not examine all types of psychiatric problems and had limitations preventing regulators "from drawing reliable conclusions."

Last year Pfizer proposed that the FDA remove Chantix's so-called black box warning based on the company's findings and other data.

The agency's update follows the recommendation of a panel of outside experts, who voted last October to keep the boxed warning on the drug until it can be reevaluated based on new information. New York-based Pfizer is expected to complete a larger study of Chantix's psychiatric side effects in late 2015.

Chantix's safety has been debated in medical journals and courtrooms since 2007, when reports of suicide, agitation and other problems first began streaming into the FDA.

The drug's labeling currently tells patients to stop taking Chantix immediately if they experience agitation, depressed mood, suicidal thinking and other behavioural changes. Doctors are advised to weigh the drug's risks against its potential benefits of helping patients quit smoking.

Pfizer's drug works by binding to the same spots in the brain that are activated by nicotine when people smoke. The drug, known generically as varenicline, blocks nicotine from binding to those spots and prevents the release of "feel-good" brain chemicals that make smoking so addictive.