Pfizer anti-smoking drug under FDA safety review

By Kim Dixon

WASHINGTON (Reuters) - The U.S. Food and Drug Administration issued an early warning on Tuesday about Pfizer Inc's anti-smoking drug, Chantix, amid reports of suicidal thoughts and behavior, and at least one death potentially linked to the medication.

The FDA is analyzing reports of erratic and aggressive behavior and suicidal thoughts and behavior in patients taking the prescription drug, known generically as varenicline.

An early agency assessment "reveals that 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, the FDA said in a posting about the new review.

Under increased scrutiny from lawmakers and consumer groups for failing to communicate safety problems with drugs in a timely manner, the FDA has started alerting the public earlier about a review, even if it has not come to a conclusion.

Many drugmakers claim the agency is taking a tougher stance on safety following the 2004 withdrawal of Merck & Co Inc's arthritis drug, Vioxx, and amid recent safety concerns about 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," said Damien Conover, an analyst at investment research group Morningstar.

But he said 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," he added.

Pfizer, the world's biggest pharmaceutical company, reported revenue of $241 million for Chantix in the third quarter of 2007. That is significant, but still not one of its major drugs. It recently launched an ad campaign touting the drug, which it began selling last year.

CAUSALITY UP IN AIR

The FDA 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 voluntarily submitted to companies by consumers and doctors and are a very rough indicator of any potential trends, a Pfizer official said.

"Postmarketing 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.

She also noted that programs to stop smoking very often lead to nicotine withdrawal, which is exacerbated in patients with psychiatric illness.

The FDA noted, however, that not all patients in the cases noted had a preexisting psychiatric illness and not all had stopped smoking.