WASHINGTON — The Federal Aviation Administration on Wednesday banned pilots and air traffic controllers from using a popular anti-smoking drug after a study found that it had apparently contributed to auto accidents and other problems that posed risks to both users and others.
The drug, marketed as Chantix, has been hailed as an innovative treatment to help smokers quit. But a study by a medical safety group -- also issued Wednesday -- linked it to a variety of unusual and serious side effects, including seizures and loss of consciousness, and prompted the FAA to act, agency spokesman Les Dorr said.
The aviation agency had approved the drug last summer, before federal safety regulators began investigating reports of serious psychiatric problems, including suicidal behavior, sharp shifts in mood and vivid nighttime episodes some patients call "Chantix dreams."
A new warning came from a report by the Institute for Safe Medication Practices, based on an analysis of "adverse events" reported to the Food and Drug Administration.
"We have immediate safety concerns about the use of [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," the study said.
It was not clear whether the Pentagon or the civilian regulatory agencies that oversee transportation would follow the FAA's example.
The study also cited other serious reported side effects, including vision problems, heart rhythm disturbances, seizures and skin reactions. The nonprofit group that conducted the study advises hospitals and doctors on the prevention of medication errors.
"These data provide a strong signal that the risks of [Chantix] treatment have been underestimated, and show that a wide spectrum of serious injuries are being reported in large numbers," the report said.
Prescription drugs are usually tested on a few thousand people before approval, but serious problems may not emerge until many more patients have used the medication for a sustained period.
Responding to the study, FDA spokeswoman Susan Cruzan said: "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."
The agency has recently issued warnings about the drug's effects on mental health, as well as the possibility that taking it could impair driving.
Manufacturer Pfizer Inc. strongly defended Chantix.
Smoking "is one of the largest problems we face in the world," said Dr. Anjan Chatterjee, a Pfizer medical director. "When you think about it in that perspective, the risk-benefit analysis is still substantially toward benefit. Even medications most people consider innocuous have side effects."
In a statement, the company said it thought that current warnings on Chantix accurately reflected the drug's risks and benefits, suggesting that no further FDA action was needed. And it cautioned that the raw data on which the safety group based its study often lacked sufficient detail to prove direct cause and effect.
Chantix has become a top seller for Pfizer since its approval in May 2006. It acts at sites in the brain affected by nicotine, easing withdrawal symptoms by providing some of the effects of nicotine and blocking those effects if smokers take up the habit again, according to the FDA.
A month's supply of the drug costs $130, and treatment can last from three to six months. More than 3.5 million people in the United States have used the drug.
Chantix gained notoriety last fall when a 34-year-old Dallas-area rock musician, Carter Albrecht, was shot to death as he pummeled a neighbor's door in the middle of the night. Albrecht's family and his girlfriend blamed the outburst on Chantix.
The medical examiner found that Albrecht was intoxicated with alcohol, but investigators were unable to test for the prescription drug. The FDA launched its own review, which led to warnings about the suicide risks.
The most recent warning, issued Friday, advised patients to stop taking Chantix and to immediately call their doctors if they experience agitation, depression, behavior changes or suicidal thoughts.
The safety group's lead researcher, Thomas J. Moore, said the FDA had not gone far enough. "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," he said. "The nonpsychiatric elements are the ones that concern us."
Moore said the concerns about Chantix came from a data-monitoring program that the group launched to help identify emerging drug risks. It tracks quarterly reports to the FDA of serious side effects that were not detected in testing before a medication's approval.