- Varenicline (Chantix) is a smoking cessation medication that is designed to reduce nicotine craving and withdrawal by slightly increasing levels of dopamine in the brain. Research has shown that varenicline is a safe, well-tolerated, and effective treatment for nicotine dependence, but researchers are interested in learning more about how it affects the brain and its function. Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) will help researchers study the brain s response to nicotine and varenicline.