Chantix and Champix, which are both manufactured by Pfizer, Inc., contain the pharmaceutical ingredient varenicline tartrate, which blocks brain receptors that are normally stimulated by nicotine. The drug is designed to lessen the pleasure effects of nicotine and help users quit smoking.

In the United States, Chantix has been associated with a number of serious and potentially life-threatening side effects, including an increased risk of suicide, suicide attempts and unusual behavior. A number of users have also report developing new-onset diabetes after taking the drug and suffering seizures and blackouts, which could result in serious accidents or injury.