Pfizer says U.S. regulators have removed a bold-letter warning from its anti-smoking drug Chantix about risks of dangerous psychiatric side effects.
The Food and Drug Administration action follows years of scrutiny into the smoking-cessation pill, which received the agency's most stringent warning in 2009 after reports of suicidal tendencies, hostility and depression among some patients.
Friday's decision stems from an 8,000-patient study of smokers that found no elevated risk of psychiatric problems among Chantix users who had no prior history of mental illness. European regulators previously removed their own warning from the drug based on the same data.
Chantix's updated label will still mention reports of psychosis, paranoia, anxiety and other problems. But those events will not be highlighted in a so-called black box warning.
Quitting smoking, with or without medication, can cause significant withdrawal symptoms, including irritability, mood swings and depression. In addition, psychiatric conditions are more common in smokers than nonsmokers.
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.
Shares of New York-based Pfizer Inc. fell 12 cents to $32.62 in afternoon trading.
