Chantix Side Effects

Chantix is the brand name of the drug varenicline, prescribed to smokers to help them quit. Produced by Pfizer Inc., Chantix affects chemical transmitters in the brain. Several common side effects can occur, and some rare but very serious negative effects have resulted in lawsuits.

Most Common Effects

In clinical trials, up to 30 percent of people taking Chantix experienced nausea, and up to 19 percent had insomnia or headaches.

Other Effects

Other common side effects, occurring in over five percent of users, include abnormal dreams, constipation, gas, abdominal pain and vomiting.

Serious Side Effects

Serious side effects involving mental illness have been reported since Chantix was approved by the United States Food and Drug Administration. These include abnormally aggressive behavior, depression, hallucinations and suicide attempts.

Mental Illness

Chantix has been linked to the onset or recurrence of psychiatric illnesses, including bipolar disorder and schizophrenia.

Expert Insight

The Institute for Safe Medication Practices (ISMP) noted that Chantix was responsible for more reports of serious negative drug events in the United States during the last quarter of 2007 than any other drug. In its 3rd quarter 2008 report, ISMP stated that Chantix use continued to generate more reports of serious psychiatric side effects than any other prescription medication, and only three prescription drugs ranked higher for causing serious injury.