Nov. 3, 2011 -- Just over a week after federal health officials released a report finding no evidence of an increased risk of serious psychiatric problems in users of the anti-smoking drug Chantix, a new study comes to the opposite conclusion.
Investigators who were the first to link the drug to suicidal behavior and depression say the new research suggests that Chantix may be too risky to use as a first treatment for smoking cessation and should only be used when other treatments have failed.
Representatives of FDA and Pfizer, the drug's manufacturer, strongly disagree with the new study findings.
Stronger Warning Needed?
The researchers found that 90% of all reported suicides related to anti-smoking treatments from 1998 to 2010 involved Chantix, even though the drug has only been on the market in the U.S. for about four years.
"We believe this drug is not suitable for use as a first choice for people who are trying to stop smoking," study researcher Thomas J. Moore tells WebMD. Moore is a senior scientist with Safe Medicine Practices, an independent drug safety research group.
They are asking the FDA to revise its labeling for Chantix to show this increased risk. But an FDA official is calling the researchers' conclusions misleading.
The new study was published online this week and appears in the November issue of PLoS One.
Conflicting Studies on Chantix
The FDA is standing by its Oct. 24 review of two FDA-sponsored studies that examined hospitalizations for psychiatric reasons in users of Chantix and nicotine-replacement therapy. But the FDA also acknowledges that the studies had significant limitations that made it impossible to rule out an increased risk of suicidal behavior and depression associated with the drug.
The studies found no evidence of an increase in hospitalizations for psychiatric reasons in Chantix users compared to nicotine patch users.
In the new analysis, Moore and colleagues from Wake Forest University, Harvard Medical School, and Johns Hopkins University School of Medicine analyzed 3,249 cases of depression and self-injury in Chantix users from 1998 to 2010, as well as users of the antidepressant Zyban, which is approved for smoking cessation, and other nicotine-replacement treatments.
The cases were reported to the FDA's Adverse Event Reporting System.
A total of 2,925 of the reported cases involved Chantix (90%), 229 occurred in Zyban users (7%), and 95 (3%) occurred in users of tobacco-replacement treatments.
In an email, FDA spokeswoman Karen Riley said much of the data used by Moore and colleagues in the new report were not new and had led to the "black box" warning that appears on the drug's labeling. A black box warning is the FDA's most serious warning.
The warning states that some people have experienced "changes in behavior, hostility, agitation, depressed mood and suicidal thoughts or actions."
Riley says the researchers failed to consider the impact of media reports linking Chantix to suicidal behaviors as early as 2007, and how that might have influenced people's reporting of similar events after this time.
Moore denies this, countering that the FDA studies were "fatally flawed" in part because they relied on hospitalization records.
"Suicide does not result in hospitalization," he says.
Under the direction of the FDA, Pfizer is conducting a new clinical trial specifically designed to examine depression and other psychiatric events in Chantix users compared to users of Zyban, nicotine replacement, and placebo in people with and without prior psychiatric problems.
Results from the study are expected to be made public in 2017.
In a written statement, Pfizer spokesman MacKay Jimeson was highly critical of the reliance of Moore and colleagues on reports that came out after the drug went to market.
"Post-marketing reports can come from any source ranging from patients to health care providers, and from phone calls to Internet postings and lawyers," he tells WebMD. "Because of the many limitations of post-marketing reports, the conclusions made by the authors are not supported by the data."