What is the most common side effect experienced while
taking Chantix or varenicline? It all depends on how you
look at it. If you surf online the answer might appear to be
nausea. Nausea is reported in about 30% of people taking
this drug.
However, sleep disturbance is much more common.
Especially if you add all the side effects having to do with
sleeping:
Insomnia 18%
Abnormal dreams 13%
Sleep disorder 5%
Somnolence 3%
Nightmares 1%
___
Total 40%
However the wild dreams cause by Chantix was actually
enjoyed by some people. So maybe its a benefit and not
a side effect per say.