06/03/2008- THE ANTI-SMOKING drug Chantix developed by Pfizer is being re- examined by the US Food and Drug Administration after reports that hundreds of patients have experienced serious problems.

Janet Woodcock, director of the FDAs Center for Drug Evaluation and Research, says the agency is reviewing all the cases. Were are looking at them, but it takes awhile.

The drug, which aims to help smokers quit their habit in part by mimicking some of nicotines effects, has already been linked to psychiatric side effects such as depression and suicide. But researchers at the nonprofit Institute for Safe Medication Practices and Wake Forest University found hundreds of reported cases of accidents, heart trouble, vision loss and other problems with Chantix since its 2006 approval.

FDAs Woodcock says the agency does not yet know whether the drug directly caused the complications cited in the researchers report.

Agency scientists are in the process of sorting through the cases. Pfizer officials have defended Chantix, a key drug for the drugmaker that has touted its potential to generate new revenue, but prescriptions for the drug have been declining, according to some analysts.

Pfizer, the drugs manufacturer, says that as early as May last year it added a warning to the prescribing literature for Chantix that patients should exercise caution when driving or operating machinery until they know how the medication affects them.

But such admonitions apparently did not get much notice from busy doctors. The FDA has received more than 3,000 reports of serious problems involving Chantix, but Pfizer says that has to be put into context, as more than five million people have taken the medication in the United States alone.

The company says that no direct cause and effect has been proved between the problems and the drug.