Bad Chantix Experience

Chantix (varenicline) is a fairly new drug designed to help people quit smoking. It also has the ability to help people with other addictions such as alcoholism. Chantix works by targeting nicotinic acetylcholine receptors in the brain. By acting as a partial agonist on those receptors it can substitute for nicotine and make smoking less rewarding. Unfortunately for Pfizer (the company selling this drug), reports have trickled in about some bad side effects. Some people have become suicidal shorty after starting the drug. A host of other weird symptoms have also been documented. I found this fascinating article about a person's experience with taking chantix. It sounds like he had an awful time while on it.

This Is My Brain on Chantix

"I wondered whether Chantix was zapping my brain’s pleasure-delivery system to such a degree that not only did I find no reward in cigarettes, but I also found no reward in socializing, exercising, writing, or any of my usual self-stimulating tricks. I’d pace the floor, sit on the bed, channel surf, pace some more, try to read, but the room had a stale, sinking feeling. Maybe I should go and grab a drink—then at least I might be able to get some rest." Derek de Koff

Not a very good report from this particular person. It looks like Chantix messes with the brains reward center and may have the propensity to exacerbate depression in susceptible individuals.
Interestingly some researchers have hypothesized that Chantix might have antidepressant properties. There is a clinical trial being done on depressed patients to see if it does. So it should be interesting to see the results of this trial to find out whether Chantix exacerbates the underlying condition or not. Antidepressants themselves have sometimes been known to increase suicidal thoughts in certain patients. So it isn't too surprising that Chantix may do this as well.

As a partial agonist Chantix binds to those nicotinic receptors, but causes less activation than a full agonist. So if you were smoking and getting nicotine, you might normally have high activation of those nicotinic receptors due to nicotines full agonistic effect. However once you start taking Chantix there could concievably be a sudden large drop in receptor activation brought about by the partial agonistic effect of the drug. This could lead to a reduction in dopamine levels in the brains reward center which might induce feelings of depression in certain individuals. So it probably depends on the change in receptor activation when going from no drug, to taking the drug. I would think that in non-smokers, Chantix would increase activation of the nicotinic receptors and lead to a reduction in depressive symptoms. However it might depend on an individuals own brain chemistry starting point and whether those receptors were activated to a greater degree or not by taking the drug.