Chantix: Quarterwatch Article
May 19, 2011
In 2006, the Pfizer product, Chantix (varenicline), was FDA-approved as a smoking cessation aid. Soon after marketing, FDA became aware through its postmarketing surveillance system, the Adverse Events Reporting System or AERS, of the potential for serious neuropsychiatric events in patients taking Chantix. Subsequently, FDA began communicating about these potential risks with health professionals and patients. A list of previous safety communications can be found on the Chantix Information page.
Amid continuing adverse event reports, in July 2009, the FDA required that Pfizer update the Chantix label with the most restrictive safety labeling - a boxed warning – describing the risk for neuropsychiatric events. This warning was directly related to the association of Chantix with suicidal thoughts and aggressive behavior. In addition, in 2008, FDA required a mandatory medication guide for patients describing this risk.
In July 2010, Pfizer, at the request of FDA, resubmitted a large number of adverse event reports that were initially sent to the Agency in a way that did not allow for comprehensive evaluation. Although this resubmission included thousands of reports of potential adverse events, these events were spread out over a number of years, and had been reported to the agency periodically in summary safety reports. These reports confirm what we already knew about Chantix and would not have changed the Agency's position on the drug's risks and benefits, given that the data in these reports were consistent with those that led to the 2009 labeling change. At this point, based on the data, FDA does not have any new safety concerns with Chantix, though those that have been established remain under active review.
The Agency takes seriously the adverse events associated with all drugs, including Chantix. FDA continues to monitor for serious and unexpected events associated with Chantix. FDA has initiated additional postmarket safety activities. Specifically, it has required the manufacturer of Chantix to conduct a large, comparative, postmarket clinical trial assessing the safety of Chantix among other smoking cessation aids. FDA has also initiated two observational safety studies on Chantix, one with the Veterans Administration and one with the Department of Defense.
Last year, FDA became aware that a few manufacturers were submitting adverse events reports to FDA through improper channels. At that time, FDA clarified its instructions to drug manufacturers, including Pfizer, to submit adverse event reports through a channel that would allow for the adverse event reports to be entered into FDA's Adverse Event Reporting System, a database of postmarketing adverse event reports that allows for review by the Agency's safety staff. These instructions were clarified and put on the FDA website for AERS Electronic Submissions.
FDA will continue to monitor the postmarket safety of Chantix and will communicate any new information as it becomes available. The Agency remains committed to monitoring the safety of drugs as they are used in the postmarket, real-world setting.