A study this week found that Pfizer’s stop smoking drug Chantix (varenicline) did not increase the risk of psychiatric events, including suicide, compared to the nicotine patch, another older drug and a placebo. The results were somewhat surprising, considering that the drug has been plagued by reports of severe mood changes, hallucinations, paranoia, anxiety, panic and suicidal ideation, to name a few side effects.
Since its approval in 2006, Chantix has been one of the most controversial drugs approved by the FDA, both because of the patient-reported side effects and questions over whether it is really more effective than existing smoking cessation therapies on the market.
Amid reports of significant psychiatric side effects, the FDA was prompted to place what is known as a “black box” warning — the most severe -– on the drug’s labeling to warn of these effects. For years, Pfizer has been trying to get the “black box” removed since it has a chilling effect on sales of Chantix.
The FDA asked Pfizer to conduct a large post-marketing study to more closely look at the psychiatric side effects. And the results of this latest trial, which was sponsored by Pfizer, have come back strongly in Chantix’s favor.
How the Study Was Conducted
The study, published in The Lancet, enrolled more than 8,000 smokers and half had a pre-existing mental illness. They were given either Chantix, Zyban (bupropion, developed by GlaxoSmithKline, but now a generic), nicotine patch and placebo. Among those without psychiatric problems, the suicide rate was quite low and similar among all the treatments.
However, among those with pre-existing psychiatric conditions, the risk of suicidal thoughts or behavior was higher -– 6.5% for those on Chantix, 6.7% for those on Zyban, 5.2% for those on the patch, and around 5% for those on placebo. Statistically speaking, the risk is considered similar in this group no matter the treatment.
Pfizer has lauded the results, seeming victorious in its efforts to prove the psychiatric side effects issue isn’t all it’s cracked up to be. The drugmaker also says it will now ask the FDA to remove the “black box.”
So, does this mean more people should take Chantix and not worry about potential psychiatric events happening? No.
“It would be a mistake to claim this study proves that severe psychiatric side effects don’t occur with Chantix,” Thomas Moore, a scientist with the non-profit Institute for Safe Medicines Practices, told STAT.
“With eight different treatment arms, the number of patients in each may not be enough to capture the severe psychiatric side effects for which the drug is known. The study’s severity assessments were subjective judgments, and the combined endpoint included many psychiatric side effects that Chantix is not suspected of causing,” he said.
This is not Pfizer’s first time trying to get that pesky “black box” warning taken off. In October 2014, the FDA held an advisory committee meeting to discuss a bunch of new studies that downplayed the psychiatric risks associated with Chantix. The studies were both observational in nature and included an analysis of existing clinical trial data. Committee members were not swayed and the black box warning has stuck.
“These studies did not show an increased risk of neuropsychiatric side effects with Chantix; however, they did not examine all types of neuropsychiatric side effects, and they had limitations that prevented us from drawing reliable conclusions,” the FDA wrote in a March 2015 drug safety announcement.
So, next time you read about a study that claims a drug is found to not have serious side effects, make sure you are getting the full picture.
Jonathan Block is MedShadow’s content editor. He has previously worked for Psychiatry Advisor, Modern Healthcare, Health Reform Week and The Pink Sheet.