The Federal Aviation Administration (FAA) says that pilots and air-traffic controllers may not use the antismoking drug Chantix, citing concerns about side-effects associated with the drug, the Associated Press reported May 21.

"We have immediate safety concerns about the use of varenicline (Chantix) among persons operating aircraft, trains, buses and other vehicles, or in other settings where a lapse in alertness or motor control could lead to massive, serious injury," said a new report from the Institute for Safe Medication Practices, which found hundreds of cases where Chantix users experienced dizziness, loss of consciousness, seizures, and abnormal movements and spasms.

A spokesperson for the FAA said that the ban would go into effect immediately even though the agency has not received any reports of Chantix being involved in aviation accidents.

Pfizer, the maker of Chantix, said that the labels on the drug already warn against operating heavy machinery or driving, and the firm cast doubt on reports of incidents of serious side effects. "It is important to understand the limitations of spontaneous adverse event reporting," the company said. "Often these reports lack sufficient medical information and/or have confounding factors that prevent a meaningful assessment of causality."