Pfizer's anti-smoking drug linked to depression

Pfizer's smoking cessation drug Chantix has run into a regulatory roadblock.

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(Fortune) -- Any smoker knows what a bummer it is to quit, but Pfizer's new smoking cessation drug may trigger depression or suicidal thoughts, the Food and Drug Administration said today.

The FDA this afternoon asked doctors to begin closely monitoring patients who are taking Pfizer's stop-smoking pill, Chantix. Agency officials say they have received a number of reports from patients and doctors that Chantix is responsible for depression, severe mood swings, abnormal dream states, and thoughts of suicide.

Since Chantix was released May 10, 2006, the FDA says it has received approximately 100 reports of adverse behavioral effects. Agency officials explain that they had been looking in reports regarding Chantix when they learned of Carter Albrecht, a Dallas man, who may have been taking Chantix at the time when he tried to kick down a neighbor's door last September. The neighbor shot and killed Albrecht. Family members claim Albrecht's raged may have been caused by Pfizer's drug. According to police reports, Albrecht had also been drinking.

Today's alert is not an order to stop prescribing Chantix - a twice-a-day tablet prescribed for 12 weeks - but rather a request to monitor patients. "We're beginning to look at this as an emerging safety issue," said FDA spokesperson Rita Chappelle. "We're requesting information from physicians, patients, nurses, and family members. This is an effort to let everyone know we're looking at the adverse events."

The agency's notification today is known as an "early communication." It is meant to alert physicians that some patients are experiencing adverse side effects with a particular treatment. The FDA has also asked Pfizer to submit any information its researchers may have pertaining to unusual behavior in patients taking Chantix. (Of course, it will be no easy task defining "unusual behavior" in people who are trying to quit smoking.)

Over four million patients have filled prescriptions for Chantix so far. Martina Flammer, a senior medical director at Pfizer, points out that the company warns patients, in Chantix's label insert, that smoking cessation--without or without medication--can lead to depressed mood and irritability. "There is no scientific evidence that establishes a causal relationship between Chantix and these reported events," said Flammer. "But we are reviewing them, and forwarding them to the FDA and other agencies."

The FDA's alert comes at a bad time for Pfizer (Charts, Fortune 500). The company's biggest drug, cholesterol-lowering pill, Lipitor, is lumbering toward patent expiration as early as 2010. Lipitor garnered roughly $13 billion in sales in 2006, more than a third of the company's overall $48.3 billion in revenue. In the meantime, Pfizer possesses a pipeline of future medicines that won't be able to fill the revenue hole left when Lipitor starts to face generic competition. Pfizer did not return calls seeking comment.

The company can ill afford safety doubts being cast on Chantix. Although sales of the drug totaled $101 million last year, analysts previously believed the drug had the potential to generate peak sales of more than a billion dollars a year. Chantix also has symbolic meaning to Pfizer. The company has been criticized for much of this decade for being better at M&A than R&D. Indeed many of the company's top-selling drugs have come to Pfizer by way of mergers, acquisitions, and joint ventures. Chantix, discovered in Pfizer's Groton, Connecticut labs, is the first potential blockbuster of Pfizer's own making since 1998's Viagra.