Following the Federal Aviation Administration’s decision to ban use of anti-smoking drug Chantix by pilots and air controllers on Wednesday, now it is the Federal Motor Carrier Safety Administration’s turn to warn against the medicine.

On Thursday, the agency urged medical examiners “to not qualify anyone currently using this medication for commercial motor vehicle licenses,” the Wall Street Journal reports.

The dramatic decisions follow a report by the Institute for Safe Medication Practices, a non-profit watchdog group based in Horsham, Pa., which warns against “use of Chantix among persons operating aircrafts, trains, buses and other vehicles, or in other settings where a lapse in alertness or motor control could lead to massive, serious injury.”

The report linked Chantix to 988 serious events in the last quarter of 2007 alone.

The drug, made by Pfizer, was approved in 2006 for sale in the U.S. and the European Union. Sales of the drug were $883 million last year and an estimated 6.5 million people have used it worldwide.

Since approval, Chantix has been under fire due to its serious side effects such as depression, suicidal thoughts, aggression, or possible psychosis. Now, the new report also found the drug responsible for potentially lethal heart rhythm disturbances, heart attack, seizures and diabetes in its users. Of special concern for those operating airplanes and trucks, there were 173 serious injuries, some resulting from traffic accidents where drivers were dizzy, mentally confused or became unconscious.

“We would not have written this report if all we had seen were the psychiatric effects, because the FDA has already issued a public health advisory on that. The nonpsychiatric elements are the ones that concern us,” lead researcher of the Institute for Safe Medication Practices, Thomas J Moore said.

Following the release of the report, Pfizer issued a statement defending the drug saying its label already contains safety warnings about driving or operating machinery. “There are few things that provide greater health benefits than quitting smoking. When considering the use of Chantix for their patients, health care providers should discuss the risks of smoking, the health benefits of quitting smoking, and the product’s efficacy and safety profile,” Francisco Gebauer, a Pfizer representative wrote in the statement, the New York Times reported.

Pfizer added new warnings to the drug’s label no further than February this year, when the FDA warned about the risk of mood and behavior changes. The warning also said Chantix could impair patient’s ability to drive or use heavy equipment.

The FDA representative Susan Cruzan said the agency was still investigating the drug’s psychiatric effects. “We agree that these findings are a signal that requires further investigation and confirmation, and the FDA has been conducting a review of the adverse events associated with Chantix.” However, an investigation into the nonpsychiatric effects of Chatix has not been initiated yet, Cruzan said.

On Friday, patients using Chantix were warned to stop taking it and to immediately call their health care providers if they experience agitation, depression, behavior changes or suicidal thoughts.

The findings of the study were posted online because its co-author Curt Furberg, a Wake Forest University Medical epidemiologist, thought the findings too important to submit to a medical journal, which could take six months or more to publish.