Chantix (varenicline) is a drug used in the treatment of smoking cessation. Chantix is used in combination with a treatment plan involving counseling or motivational strategies to help patients quit smoking. Common side effects associated with Chantix use include nausea, constipation, gas and heartburn.Chantix is a medicinal system used to help patient's quit smoking. The active ingredient used in the pack is varenicline, which is a partial agonist at nicotine receptors. What this means is that patients feel the effects of nicotine, but at a lesser dose than if smoked. This helps patients slowly come off smoking in a gradual way, thereby reducing withdrawal effects. The Chantix comes with the active ingredient at different doses. For example, for the first three days, patients take 0.5mg once daily. From days 4-7, patients take 0.5mg twice daily, and from days 8 until the end of treatment, patients take 1mg twice daily. Patients are advised not to exceed this dose as it may disturb the smoking cession process and increase withdrawal effects.