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Trade/other name(s): Chantix, Champix (in the UK)

Why would this drug be used?

Varenicline is used to help people quit smoking.

How does this drug work?

Varenicline binds to the nicotine receptors in the brain, and blocks them so that nicotine cannot bind to them. The reward of nicotine is reduced because nicotine can no longer stimulate the pleasure center by raising the dopamine level in the brain. This helps reduce cravings for cigarettes. It also seems to help reduce withdrawal symptoms when smokers quit.

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, or foods.
  • If you have heart problems or blood vessel (circulation) problems. Some types of heart and blood vessel problems might be made worse by this drug (see “Precautions” below).
  • If you have other serious medical problems, especially kidney disease.
  • If you have ever had depression, bipolar illness, schizophrenia, or other serious mental health problems. Varenicline has not been tested in large groups of people with these illnesses, and the safety of the drug is not clear when a person has a serious mental illness. Some research suggests that people who are stable on antidepressants seem to do well on Chantix, although these studies didn’t include people taking bupropion (Wellbutrin, Zyban).
  • What kinds of symptoms you’ve had when you’ve tried to quit smoking in the past.
  • If you’ve ever had seizures. This drug might raise your risk of having them again (see “Precautions”).
  • If you drink alcohol. In some people, varenicline increases its effects (see “Precautions”).
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. Although studies in pregnant animals show no problems, studies in pregnant women have not been done. Varenicline may be used only if the potential benefit outweighs the risk to the fetus.
  • If you are breast-feeding. Some animal studies have shown that varenicline may be transferred to nursing pups. While no human studies have been done, this drug may pass into breast milk and affect the baby. Talk with your doctor about the possible risks of breast-feeding while taking this drug.
  • About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

Some drug doses may need to be changed when you stop smoking. Talk with your doctor about this.

In some people, this drug can increase the effects from alcohol. (See “Precautions.”)

No other major drug interactions are known at this time. However, people who used nicotine patches at the same time they used varenicline tended to have more side effects such as stomach trouble, tiredness, dizziness, and headache.

You may want to check with your doctor, nurse, or pharmacist about any new information on whether any medicines, vitamins, herbs, and supplements can cause problems with this medicine.

Interactions with foods

You can have increased effects from alcohol while on this medicine. If you drink, you’re more likely to have memory blackouts (amnesia) or other problems while taking varenicline. No other serious interactions with foods are known at this time. Check with your doctor, nurse, or pharmacist about whether foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Varenicline is a pill. It should be taken after a meal, with a full glass of water. For the first 3 days, the dose consists of a single 0.5 milligram (mg) tablet. For the next 4 days, one 0.5 mg tablet should be taken each morning and evening. Starting with the second week, the dose is a 1 mg tablet each morning and evening. Some people have problems with this higher dose. If you do, talk to your doctor about using a lower dose.

Varenicline is typically started a week before the planned stop-smoking date, and is taken for 12 weeks. Other people start taking varenicline and then choose a quit date between the 8th and 35th days of taking the drug. People who are able to quit smoking during the first 12-week period may keep taking it for another 12 weeks of treatment to improve their chances of staying quit. Those who are not able to quit during the first 12 weeks may want to address any factors that made it harder for them to quit, and then try again.


Some people have nausea and trouble sleeping at first, which usually goes away on its own. However, if you keep being troubled by these symptoms, talk with your doctor. You may do better on a lower dose of the drug.

Some people feel sleepy, dizzy, or have trouble concentrating while taking varenicline, and traffic accidents have been reported in people taking this drug. Use caution when driving or operating machinery until you know how varenicline will affect you.

Some people have reported emotional changes such as depressed mood, agitation, panic, changes in behavior (including hostility and aggressiveness), paranoia, confusion, homicidal thoughts, suicidal thoughts, and even suicide attempts while using varenicline to try and quit smoking. If you have any of these symptoms, stop taking the drug and contact your doctor right away. Note that in some people these symptoms persist for a while after the drug is stopped.

There are reports of heightened alcohol effects, with problems such as unusual, aggressive, or violent behavior and memory blackouts (temporary amnesia) in some people. If you drink, reduce your alcohol intake until you know whether varenicline affects your alcohol tolerance.

Tell family members, loved ones, and caregivers when you plan to start taking this drug. They should know to contact your doctor right away for mood and behavior changes. This is important, since another person may be able to better see changes that are not caused by nicotine withdrawal.

Some people are allergic to varenicline and may have symptoms like swelling of the face, lips, mouth, tongue, or throat, and may notice trouble breathing or swallowing. Stop the drug and get medical help right away if you have any of these symptoms.

Rarely, people can have seizures due to this medicine, usually within the first month of starting it.

While taking this medicine, and for a few days afterward, there is a slight chance of a serious skin reaction that can be life-threatening (Stevens-Johnson syndrome or erythema multiforme). It can start as a rash with redness or blistering in the mouth, nose, or eyes that can spread to the skin, along with fever and body aches. If this starts to happen, stop the drug and get medical help right away.

People with some types of heart or blood vessel diseases are at slightly higher risk of having symptoms or worse problems while on varenicline. Call your doctor if you have trouble breathing, shortness of breath, or chest pain, symptoms of a stroke (such as weakness on one side of the body, trouble walking or speaking, or numbness), or if you have any new or worse pain in your legs when walking.

It is not unusual to feel irritable, anxious, somewhat depressed, or have trouble sleeping when you are withdrawing from nicotine, whether or not you take varenicline.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.


  • Nausea*

Less common

  • Headache
  • Trouble sleeping*
  • Vivid, strange, or unusual dreams
  • Increased effects of alcohol*


  • Change in how things taste
  • Vomiting
  • Abdominal (belly) pain
  • Upset stomach
  • Flatulence (passing gas)
  • Constipation
  • Depressed mood*
  • Agitation, restlessness*
  • Change in behavior, including hostility and aggressiveness*
  • Thoughts of suicide, suicide attempts*
  • Allergic reaction with swelling in mouth or throat, trouble breathing or swallowing*
  • Serious rash that can cause skin blistering*
  • Chest pain or heart attack*
  • Seizures (convulsions)*
  • Circulation problems (new or worse than before), such as pain with walking*
  • Death due to suicide or aggressive behavior

*See “Precautions” section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved in 2006.

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 12/02/2014
Last Revised: 12/02/2014