Chantix, already linked to suicide, has been tied to other serious side effects. Once considered a success for Pfizer Inc., the smoking cessation drug could soon be a drag on the drugmaker. Many analysts had predicted that Chantix sales could hit $2.28 billion by 2012. But now, the drugs troubles have some rethinking those rosy prognostications. Some analysts have already said forecasts for Chantix sales could be downgraded by as much as 30 percent. Unfortunately for Pfizer, Chantix is the company’s second biggest growth driver, after Lyrica, a drug for fibromyalgia.

Chantix is the first such nicotine receptor partial agonist approved by the Food & Drug Administration (FDA). It was heralded as an alternative to other smoking cessation drugs and nicotine replacement therapy. But since its approval, Chantix has been linked to a number of disturbing side effects. Last Tuesday, the Institute for Safe Medication Practices issued a report detailing Chantix adverse event repots to the FDA. The report specifically cited 224 reports of potential heart-rhythm disturbances, 372 reports of possible movement disorders and 544 reports of likely glycemic problems, including diabetes. There were also reports of traffic accidents and falls linked to Chantix. The Institute’s report has already gotten the attention of the Federal Aviation Administration, which has banned its use by pilots and air traffic controllers.

In the US, 34 Chantix users have reportedly committed suicide. According to an FDA Nov. 20 Early Communication, the agency said that its preliminary assessment revealed that many of the cases reflected new-onset of depressed mood, suicidal ideation, and changes in emotion and behavior within days to weeks of initiating Chantix treatment. In February, the FDA said “it appears increasingly likely that there may be an association between Chantix and serious neuropsychiatric symptoms.” The agency said that it had asked Pfizer to elevate the prominence of safety information regarding suicidal thoughts and other psychiatric problems to the warnings and precautions section of the Chantix prescribing information, or labeling.