Varenicline (trade name Chantix in the USA and Champix in Europe, Mexico, Canada and Australia, manufactured by Pfizer, usually in the form of varenicline tartrate) is a prescription medication used to treat smoking addiction. Varenicline is a nicotinic receptor partial agonist. In this respect, it is similar to cytisine and different from nicotinic antagonist, bupropion, and nicotine replacement therapies (NRTs) like nicotine patches (commonly, "the patch") and nicotine gum. As a partial agonist, it both reduces cravings for and decreases the pleasurable effects of cigarettes and other tobacco products, and through these mechanisms, it can assist some patients in quitting smoking.