“Based on a review of the cases, there appears to be a syndrome of debilitating symptoms that interfere with people’s ability to function in their daily lives that is associated with the use of Chantix,” Dr. Winchell said.
The company agreed that the spontaneous reports in late 2007 raised concerns about whether the drug was associated with an increase in serious neuropsychiatric events. But since 2009, this issue has been evaluated in controlled studies, which “consistently show no evidence of an increased risk,” Dr. Christopher Wohlberg, the head of Pfizer’s safety surveillance and risk management group, told the panel.
These include a meta-analysis of adverse events in 18 controlled studies of about 5,000 patients treated with varenicline and about 3,500 on placebo, which found no significant difference in the rate of neuropsychiatric events (with the exception of sleep disorders and disturbance) among those on the drug vs. those on placebo; and a meta-analysis of 5 placebo-controlled studies that used the Columbia-Suicide Severity Rating Scale to evaluate suicidal ideation and behavior, which also found no significant differences between the two groups.
In addition, four observational studies that included patients with psychiatric illnesses showed that the rates of serious neuropsychiatric events in patients treated with varenicline were not significantly different from those treated with nicotine replacement therapy or bupropion for smoking cessation. In individual studies of patients with psychiatric illnesses (schizophrenia, schizoaffective disorder, or major depressive disorder), no evidence was found of an increased risk among those treated with varenicline, compared with those on placebo, according to the company.
But the FDA reviewers raised issues with the meta-analysis of the 18 studies and the observational data. The observational data have limitations and “preclude” a conclusion that there is no association of varenicline and an increased risk of neuropsychiatric events, said Natasha Chen, Ph.D., an epidemiologist in the FDA’s office of surveillance and epidemiology. The ongoing postmarketing safety trial “is likely to offer better insights into varenicline’s neuropsychiatric risks,” she added.
The one panelist who voted to remove the warning, Dr. Andrew J. Saxon, said while there “may be some serious adverse or neuropsychiatric effects, the data, while not perfect,” do not show a signal in his view. He added that in his experience working daily with patients who are trying to quit smoking, “patients are afraid to take this medication because of the boxed warning, and it does deter use.” Moreover, in the Veterans Affairs system, there are restrictions on prescribing the drug because of the boxed warning, including a limitation on prescriptions to a 28-day supply, with no refills. Such restrictions increase hassles for patients and prescribers, and often result in patients stopping treatment after 4 weeks.
“If I’m doing a good job as a physician, I’m going to monitor the patient,” said Dr. Saxon, director of the addiction psychiatry residency program, University of Washington, Seattle.
The FDA usually follows the recommendations of its advisory panels, which are not binding. Members of these two panels had no conflicts to disclose. Occasionally, panelists with a conflict are given a waiver, but not at this meeting.
In a statementissued by Pfizer after the meeting, Dr. Steven Romano, senior vice president and head of the medicines development group for Pfizer, said the “completion of our currently ongoing safety study will represent one more step forward in the process of accurately characterizing the neuropsychiatric safety of this important medication.”
The varenicline label is available at http://labeling.pfizer.com/ShowLabeling.aspx?id=557. Serious adverse events associated with this drug should be reported to the FDA’s MedWatch program at http://www.fda.gov/Safety/MedWatch/default.htm.