Chantix (Champix outside the US) is the brand name for varenicline, a prescription medication that was created to treat tobacco addiction. It received FDA approval in May 2006, and has been used by millions of people to quit smoking. Varenicline makes it two to three times more likely for someone to have a successful quit, as compared to not taking any quit medication.
Medical review: Nathan Cobb, MD, September 26, 2017
Fiore MC, Jaén CR, Baker TB, et al. Treating Tobacco Use and Dependence: 2008 Update. Clinical Practice Guideline. Rockville, MD: U.S. Department of Health and Human Services. Public Health Service. May 2008.