In the past five years, the Food and Drug Administration (FDA) has received reports implicating the smoking cessation drug Chantix in 544 suicides and 1,869 attempted suicides, according to documents obtained by Al Jazeera America.

Since its introduction to the U.S. market in 2006, Chantix has been linked to an array of adverse psychiatric events, including suicidal behavior, depression, psychosis, and aggression. In 2008, senior researcher Thomas J. Moore of the Institute for Safe Medical Practice concluded that the drug was associated with more adverse effects than any other medication on the market. A concomitant health advisory released in May 2008 eventually prompted the Federal Aviation Administration (FAA) and the U.S. Department of Defense (DoD) to ban the drug among pilots and air traffic controllers.

“There were side effects that made it look like it was unsafe for pilots and people in critical occupations because there were seizures, blackouts, temporary blindness, blurry vision,” Moore said, speaking to Al Jazeera America. He also cited an alarming number of “inexplicable and unprovoked” episodes of violence associated with the drug. “These cases had three striking characteristics,” Moore said, referring to reports received by the FDA. “First, the violence was absolutely unpredictable and senseless. Second, the victim was anybody who happened to be nearby. It could have been a fiancé. It could have been a mother. It could have been a police officer. And third, these people had no history of violence and were unlikely prospects for a violent act.”

That said, FDA has so far been reluctant to indicate a distinct causal relationship between adverse psychiatric events and Chantix, which is distributed in the U.S. by Pfizer Inc. In a safety review released last year, the agency noted that while reports of alarming side-effects have been filed regularly, it is exceedingly difficult to determine whether these actually resulted from Chantix use. The review cited two independent studies that both failed to establish a heightened risk of neuropsychiatric hospitalization among users. “However, both studies had a number of study design limitations, including only assessing neuropsychiatric events that resulted in hospitalization, and not having a large enough sample size to detect rare adverse events,” agency officials noted.

Study limitations notwithstanding, the FDA concluded that the benefit-risk profile of Chantix was unchanged, and recommended that the drug remain on the market under its current “black-box warning” – the most serious health warning the agency issues. Some would argue that the health warning, which lists as side-effects most adverse events reported to the agency, is an adequate precautionary measure that informs patients and physicians about the drug’s psychiatric influence. Others assert that it is unrealistic to believe that formal warnings will curb the incidence of suicides.

“The use of a black box warning is to help physicians identify early symptoms that so that you can prevent the adverse event from occurring,” Michael Siegel, a professor at Boston University’ School of Public Health, told reporters. “In the case of Chantix, the black box warning is basically telling physicians, ‘Be careful because your patients might die taking this.’ What use is it to monitor patients for suicide? Once they commit suicide, it’s over.”