The FDA is currently examining reports of side-effects such as erratic and aggressive behavior and suicidal thoughts and behavior . The drug is known generically as varenicline.
The FDA was quoted :" Many of the cases reflect new-onset of depressed mood, suicidal ideation (thoughts) and changes in emotion and behavior within days to weeks of starting treatment" , in a recent posting about the new review.
As lawmakers and consumer groups step on the pressure for failing to communicate safety problems with drugs regularly , the FDA has started alerting the public earlier about a review, even if it has not come to a conclusion.
According to many drug manufacturers , the agency is taking a tougher stance on safety following the 2004 withdrawal of Merck & Co Inc's arthritis drug, Vioxx and recent safety concerns surrounding GlaxoSmithKline Plc's diabetes drug, Avandia.
"My first thought is this is another example of the FDA being overly safety conscious in light of the withdrawal of certain products, such as Vioxx and Avandia," Damien Conover, an analyst at investment research group Morningstar, was quoted. Yet he agreed that it could still be a problem for Chantix.
"When the (attention deficit disorder) drugs got associated with increased risk of suicidal thinking, you definitely saw a class effect of slower growth," Conover added
Pfizer had reported revenue of $241 million for Chantix in the third quarter of 2007. It has been just recently that the company launched an ad campaign touting the drug.
Meanwhile the FDA has stressed the warning "does not mean that FDA has concluded that there is a causal relationship between the drug and the emerging safety issue."
Adverse event reports following a drug's approval are submitted to companies by consumers and doctors. Yet, these are very rough indicators of any potential trends, a Pfizer official was reported.
"Post-marketing reports usually do not allow you to establish a causality because there is very often a significant amount of information missing," said Martina Flammer, a senior medical director at Pfizer
Flammer also observed that programs to cease smoking very often lead to nicotine withdrawal, which could be exacerbated in patients with psychiatric illness.
Yet the FDA noted that not all patients in the cases had a preexisting psychiatric illness and not all had stopped smoking.
In its alert, the FDA has cited one case of a patient whose erratic behavior while on the drug lead to death. However, it did add that alcohol was also involved.
Doctors have been advised to monitor patients taking the drug for changes in behavior and mood.