Chantix is the brand name for the drug varenicline, which is used to help people stop smoking. Chantix was approved by the Food and Drug Administration in 2006.
Function of Chantix
Chantix is a nicotine agonist. This means that it works on the same receptors in the nervous system that nicotine does. Chantix blocks the receptors and slightly stimulates them. It decreases the withdrawal symptoms and cravings that people experience when they quit smoking. Since Chantix does not stimulate these receptors as strongly as nicotine, people who smoke while taking Chantix will not find smoking as pleasurable as they did without the drug.
Nicotine in the Central Nervous System
Nicotine binds to special receptors in the central nervous system. When it binds to these receptors, it triggers the release of several chemicals called neurotransmitters into the central nervous system. One neurotransmitter, dopamine, is released in the reward center of the brain. This triggers the pleasurable sensation smokers get while smoking, and is responsible for the addictive quality of nicotine.
There are different kinds of nicotine receptors located at different areas of the central nervous system. Chantix binds to four of them, but it forms the strongest bond with the alpha-4-beta-2 nicotinic receptor in the brain. It stimulates this receptor, but does not stimulate it as strongly as nicotine does. This decreases the severity of nicotine withdrawal and blunts the pleasurable sensation smoking previously brought.
Effectiveness
In clinical trials conducted by Pfizer, 45 to 50 percent of people taking Chantix were not smoking at the end of 12 weeks, compared to only 12 percent of those taking a placebo, or sugar pill. At follow-up interviews 40 weeks later, 20 percent of the people who had taken Chantix were still not smoking. In comparison studies, Chantix had a better success rate than bupropion SR.
Behavior Changes
Chantix has been linked to suicide, suicidal thoughts and erratic behavior. It is not yet known whether this is caused by nicotine withdrawal, underlying psychiatric conditions or the drug itself. Depression, difficulty sleeping, irritability and nervousness are all symptoms of nicotine withdrawal.
Chantix was not studied in people with psychiatric conditions before its release. Since people with conditions like schizophrenia and clinical depression are more likely to smoke and have a harder time quitting smoking, these side effects may be the result of underlying psychiatric conditions that were made worse by nicotine withdrawal. Alcohol use may also be a factor in many of these reports.
In 2009 the FDA required Pfizer to issue a black box warning, its strongest warning, about these potential problems with Chantix. According to the warning, people who take Chantix should be observed for "neuropsychiatric symptoms including changes in behavior, hostility, agitation, depressed mood, and suicide related events, including ideation, behavior, and attempted suicide." If you take Chantix and experience any of these symptoms, you should stop taking the medication and contact your doctor.
References
- Chantix Prescribing Information
- Pharmacist's Letter/Prescriber's Letter; Behavioral Side Effects With Varenicline; November 2007
- Japense Journal of Pharmacology; Neuronal Nicotinic Receptor and Psychiatric Disorders: Functional and Behavioral Effects of Nicotine
