Certain side effects have been witnessed on using champix, these are: nausea; stomach pain; indigestion; vomiting; constipation; gas; weakness; fatigue; increase in appetite; unpleasant taste in mouth; headache; and insomnia and unpleasant dreams. Less serious side effects are more likely, or you may have none at all.
Champix can cause persistent nausea for a few months. Talk to your doctor about any side effects that seem unusual or become aggravated. If you have any allergic reactions like difficulty in breathing, swelling of face, lips, tongue or throat, immediately consult your medical practitioner.