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.
