Chantix, the anti-smoking drug marketed by Pfizer, Inc., has been linked to 107 adverse reactions in Canada. According to the country’s regulatory agency, Health Canada, nearly half of those reports involved psychiatric behavior. In fact, at least seven people in that country - where Chantix is sold as Champix - became suicidal while taking the drug. Though Pfizer recently modified the Chantix label to make information on psychiatric side effects more prominent, Health Canada said it saw no reason at this time to issue a Champix public health advisory. Such an advisory was issued by the US Food & Drug Administration (FDA) in February.
Chantix, approved in the US in 2006, works by blocking nicotine receptors to the brain. Chantix is the first such nicotine receptor partial agonist approved by the FDA. It was heralded as an alternative to other smoking cessation drugs and nicotine replacement therapy.
In the US, 34 Chantix users have reportedly committed suicide. According to an FDA Nov. 20 Early Communication, Pfizer had submitted several postmarketing cases to the agency describing suicidal thoughts and occasional suicidal behavior possibly linked to Chantix use. At the time, the FDA said that its preliminary assessment revealed that many of the cases reflected new-onset of depressed mood, suicidal ideation, and changes in emotion and behavior within days to weeks of initiating Chantix treatment. The role of Chantix in these cases was not clear, the FDA said, because smoking cessation, with or without treatment, is associated with nicotine withdrawal symptoms and has also been associated with the exacerbation of underlying psychiatric illness. However, not all patients described in these cases had pre-existing psychiatric illness and not all had discontinued smoking.
In February, the FDA said “it appears increasingly likely that there may be an association between Chantix and serious neuropsychiatric symptoms.” The agency said that it had asked Pfizer to elevate the prominence of safety information regarding suicidal thoughts and other psychiatric problems to the warnings and precautions section of the Chantix prescribing information, or labeling. In addition, the FDA said it was working with Pfizer to finalize a Medication Guide for patients.
In Canada, 46 Champix side effect reports involved psychiatric reactions including aggression, depression and suicidal thinking. Others involved amnesia, abnormal dreams, anxiety, insomnia, and abnormal thinking. Seven people experienced “suicidal tendency” while on Champix. Four had no personal history of a psychiatric illness, including a 33-year-old woman who became suicidal 11 days after starting the drug, according to the most recent issue of Health Canada’s Canadian Adverse Reaction Newsletter. One woman had a history of mental illness. In the remaining two cases, their psychiatric histories were not known. No Champix users in Canada have actually committed suicide, the agency said.
Despite such reports, Health Canada is not planning any public communication on Champix psychiatric side effects at this time. The reports are based on suspicion only, the agency said, and not considered scientific proof of a drug’s effect. But it’s believed only about one percent of adverse drug reactions are reported under Canada’s voluntary reporting system. Health Canada said it’s reviewing Champix and will “take appropriate action as considered necessary.”
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