Chantix (varenicline) has side effects when used. Chantix can also case serious neuropsychiatric events, including but not limited to depression and suicidal ideation, behavior changes, hostility, and agitation. Chantix can also interact with other medications, including insulin, asthma medicines and blood thinners. Anyone with an allergy or hypersensitivity to varenicline (Chantix) should also avoid using it. People with renal impairment should only use Chantix with caution. Chantix is not recommended for use in patients under 18 years of age. All questions regarding Chantix side effects should be directed to one’s medical provider and pharmacist.