FDA: Boxed warnings required for Pfizer's Chantix, GlaxoSmithKline's Zyban

The FDA announced Wednesday that it will require Pfizer and GlaxoSmithKline to include a boxed warning on their respective smoking cessation products, Chantix (varenicline) and Zyban (bupropion), about the risk of "serious mental health events, including changes in behaviour, depressed mood, hostility, and suicidal thoughts."

Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, commented that "the risk of serious adverse events while taking these products must be weighed against the significant health benefits of quitting smoking."

The decision was based on a review of adverse events reported to the agency, as well as on an analysis of clinical trial data and scientific literature, the FDA said. According to its analyses, some patients prescribed the treatments reported experiencing unusual changes in behaviour, depression, and thoughts of suicide or dying. "In many cases, the problems began shortly after starting the medication and ended when the medication was stopped," the agency noted.

The regulator said that similar information on mental health events will be required for all bupropion products. The agency will also require manufacturers to conduct a study to determine how frequently serious neuropsychiatric symptoms occur in patients using various smoking cessation therapies.

In a separate statement, Pfizer indicated that it updated the US labelling for its product in accordance with the FDA's request to highlight serious neuropsychiatric events. Chantix generated sales of $846 million in 2008. Meanwhile, a GlaxoSmithKline spokeswoman said the company has been reviewing all reports of suicides and suicidal thoughts in patients prescribed Zyban, and has already updated the drug's label to warn about suicidal thinking. She added that the drugmaker does not consider Zyban to be the direct cause of those side effects.

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