Back in November 2006 when the FDA published its initial findings, they were only able to state a potential-but still unclear-link between the use of Chantix and severe alterations in mood and behavior. Now, "potential" has moved up to an "increasingly likely association." In post-market reports, the FDA received claims of 37 suicides and over 400 incidences of suicidal behavior relating to the use of Chantix.
Pfizer, the manufacturer of Chantix, agreed to update the warning and precautions section in its prescribing information for doctors, caregivers and patients. Pfizer now includes in its warning information that "Serious neuropsychiatric symptoms have occurred in patients being treated with Chantix..." and that "All patients being treated with Chantix should be observed for neuropsychiatric symptoms including changes in behavior, agitation, depressed mood, suicidal ideation and suicidal behavior. These symptoms, as well as worsening of pre-existing psychiatric illness, have been reported..."
Pfizer also emphasized in the same warning section that no direct link has been established between its product and these side-effects; and, further, that mood changes may be a symptom of nicotine withdrawal alone.
One area in the warnings section stands out: the caution noted specifically for patients with schizophrenia, bipolar disorder, and major depressive disorder, as the safety of Chantix has not been established for persons with these illnesses. The safety has not been established because persons with these illnesses were not included in their studies. That is a choice to exclude millions of people. Call me a skeptic, but I think this exclusion was intentional. For the FDA to not take into account the notable exclusion of persons with psychiatric illness in clinical trials is hard to ignore, particularly for a drug that increases dopamine levels.
Nicotine, Dopamine and Chantix
When nicotine enters the body, it attaches to receptor sites in the brain that then release dopamine. Dopamine (a hormone, neurotransmitter, and neurohormone) is associated with several sensations (pleasure, love, addiction, motivation) and important brain functions (behavior and cognition, motor activity, motivation and reward, sleep, mood, attention, and learning).
The way Chantix works is to block the nicotine from attaching to the receptor sites (thus blocking the sensation of pleasure associated with smoking). Chantix also provides a low dose of dopamine to off-set the withdrawal symptoms (irritability, etc.).
When Pfizer obtained FDA approval for Chantix in May 2006, the FDA knew that the participants in the clinical trials did not include anyone with a psychiatric illness or a psychiatric illness history. I realize there is a push on the FDA to approve medications faster to get them to market. But these post-market psychiatric risk findings should not be surprising. Too much is already known and established about the role of dopamine in psychiatric illness treatment.