From Pharmacy Drug Guide
Chantix® (varenicline) is a prescription medication used to help patients quit smoking tobacco. Chantix® works by reducing cravings for nicotine and by reducing the pleasurable feelings from smoking.  While Chantix® may produce cardiovascular side effects, the benefits of quitting smoking may outweigh the risk of side effects from the use of Chantix®.
|Brand name for||Varenicline|
|Uses||Used to help quit smoking, may be used to help quit other addictive drugs |
|Common side effects||Nausea, constipation, gas, vomiting, excessive sleepiness, dizziness, loss of consciousness, sleep problems, or vivid, unusual, or strange dreams |
|Major side effects||Suicidal thoughts or behavior, cardiovascular events, allergic reactions including skin rash |
|Warnings||Some people have had changes in behavior, hostility, agitation, depressed mood, suicidal thoughts or actions while using Chantix® to help them quit smoking.|
|Disclaimer||The information provided by PharmacyDrugGuide.com is not a substitute for professional medical advice, diagnosis, or treatment. Do not take any action based on the information on this page without consulting a physician.|
Chantix® is a nicotine receptor partial agonist. Nicotine attaches to receptors in the brain, causing the brain to release dopamine, which gives the smoker a feeling of pleasure. Chantix® attaches to these nicotine receptors, so that even if a patient smokes cigarettes while taking Chantix®, nicotine is unable to attach to the receptors in the brain. Less dopamine is released, and smoking becomes less rewarding. This may help smokers to quit.
Chantix® is manufactured by the pharmaceutical company Pfizer, Inc., and was first approved by the FDA in 2006. Individuals beginning a Chantix® treatment are prescribed treatment one week before they intend to quit smoking.
Most patients taking Chantix® do not experience pleasurable effects which might increase the risk of abuse. Additionally, higher doses of Chantix® have been known to cause nausea and vomiting. For these reasons, Chantix® is not commonly abused. Very little data is available on Chantix® overdose.
Chantix Side Effects
Common side effects associated with Chantix® include nausea, constipation, gas, vomiting, headaches, sleep problems, and vivid, unusual, or strange dreams. Some patients also reported somnolence (excessive sleepiness), dizziness, or loss of consciousness which affected their operation of a vehicle.
More serious side effects may include psychiatric events, cardiovascular events, and allergic reactions including swelling of the face or throat, and skin rash. According to Pfizer, patients who experience suicidal thoughts or behavior should contact their doctor immediately.  
Chantix and Addiction
Two new studies have been published which suggest that Chantix® may be useful in treating cocaine and alcohol dependence. Chantix® seems to work in these patients in the same way that it works for patients who are quitting smoking. Patients found cocaine use or drinking less enjoyable. Cocaine users were half as likely to use cocaine when taking Chantix®. While results are promising, however, more studies are needed.