Varenicline Champix

Authored by , Reviewed by Prof Cathy Jackson | Last edited | Meets Patient’s editorial guidelines

If you want to stop smoking, taking varenicline (trade names Champix® and Chantix®) is likely to more than double your chance of success.

Editor's note

Dr Krishna Vakharia 9th August 2022

Varenicline (known as Champix®) is not currently available in the UK or Europe. It may not be available long-term. There has been an impurity found in the medicine leading to its recall and withdrawal, as a precaution. See Further Reading below.

Varenicline or Champix is a medicine that helps people to stop smoking. The majority of people who smoke would like to stop. One of the main reasons that many struggle to quit is that nicotine, which you breathe in when you smoke, is addictive. Soon after your last smoke, you start to have withdrawal symptoms. This is where varenicline (Champix®) can help.

You can read more about nicotine addiction and how addicted you might be in the separate leaflet called Quit Smoking (Smoking Cessation).

Varenicline (Champix®) is a medicine that was first licensed in the UK in December 2006. Champix was developed to help smokers to stop smoking. Varenicline mimics the effect of nicotine on the body. Therefore, it both reduces the urge to smoke and relieves withdrawal symptoms.

The precise action of varenicline is that it interferes with the receptors in the brain that nicotine stimulates. (The nicotine in cigarettes attaches to receptors in brain cells to stimulate part of the brain - this is how nicotine has its effect.) What varenicline does is to partly stimulate the nicotine receptors. This mimics the effects of nicotine, to reduce cravings and withdrawal effects when you stop smoking. However, at the same time, Champix partially blocks the receptors and prevents nicotine from attaching to the receptors. This blocks or blunts the effect of nicotine in people who give in to temptation and have a cigarette.

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Varenicline does increase the chance of quitting smoking. Some studies have looked at this issue. The studies compared varenicline to a dummy (placebo) tablet in people who were keen to stop smoking. The results from the studies showed that, on average, about 21 in 100 people who took varenicline successfully stopped smoking. This compared to about 8 in 100 who took the dummy tablets. In other words, taking varenicline more than doubled the rate of success.

Varenicline does not make you stop smoking. You still need determination to succeed and to break the smoking habit. A combination of varenicline with counselling from a nurse, doctor, pharmacist or other health professional is likely to increase your chance of successfully stopping smoking. Therefore, most doctors will only prescribe varenicline to people who really want to stop smoking as part of a stopping smoking programme.

  • You need a prescription to obtain varenicline - you cannot buy it at pharmacies.
  • Decide on a quit date - the date you intend to stop smoking.
  • Start taking the tablets one week before the quit date. The aim is to build up the dose so your body becomes used to the medicine before the quit date. The usual advice is to start with 0.5 mg daily for the first three days. Then 0.5 mg twice daily on days four to seven. Then, 1 mg twice daily for 11 weeks.
  • Take each dose of Champix with a full glass of water, preferably after eating. So, ideally, after breakfast and after your evening meal.
  • Tell your doctor if you develop any side-effects. A reduction in dose may be an option if the side-effect is not serious.

The usual course of treatment is for 12 weeks. If you have successfully stopped smoking by this time:

  • In many cases, treatment is stopped and that is it. You are a non-smoker!
  • In some cases, an additional 12 weeks of treatment may be advised. You can discuss this with your doctor. It may be useful for people who are not confident when off the cigarettes.
  • In some cases, a short tapering off of the dose over a week or so may be helpful. This is because at the end of treatment, if the medicine is stopped abruptly, in about 3 in 100 people there is an increase in irritability, an urge to smoke, depression and/or sleeping difficulty for a short time. These problems can be eased by a gradual reduction of dose.
  • If you have not succeeded in quitting after 12 weeks there is no point in continuing with treatment at this time. Perhaps it is best to discuss things with your doctor or practice nurse as to your future options.

Most people who take varenicline do not develop any side-effects, or they are only minor. However, it is strongly advised that you read the information that comes with the medicine for a full list of possible side-effects and cautions. The following highlights the most common and the most potentially serious side-effects of Champix

Common but not usually serious side-effects

The most commonly reported side-effect is feeling sick (nausea). This is often mild and tolerable. Nausea is thought to be less of a problem if you take the tablets just after a meal with a full glass of water. Some other reported side-effects that occur in some people include difficulty sleeping (insomnia), abnormal dreams, headaches and wind (flatulence). Taking the evening dose after your evening meal, and not just before bedtime, is thought to reduce any sleep-related side-effects.

Varenicline may also affect your ability to drive and your ability to use machines. You should not drive and you should not operate complex machinery, or take part in potentially hazardous activities, until you know how varenicline affects you.

A possible increase in the risk of heart problems

In June 2011 the US Food and Drug Administration (FDA) posted a warning that varenicline may increase the risk of heart complications (such as a heart attack) in people who have existing cardiovascular disease. (Cardiovascular disease means diseases of the heart or blood vessels, such as angina or peripheral arterial disease.) The warning was based on a research study that followed 700 smokers with cardiovascular disease who were treated with varenicline or dummy (placebo) tablets. The results of the study confirmed that varenicline was effective in helping people to quit smoking. Also, that adverse events of cardiovascular such as heart attack were uncommon overall. But, certain cardiovascular events, including heart attack, occurred slightly more frequently in people who took varenicline compared with those treated with placebo.

However, the increased risk of cardiovascular events was not statistically significant. (That is, the small increased number of cardiovascular events could have happened by chance.) More recent research has found no evidence that varenicline causes an increase in cardiovascular events such as a heart attack.

Mood and behavioural changes

Following its introduction, there were various reports of a possible link between varenicline and behavioural or mood changes. The suspected symptoms included hostility, agitation, depressed mood, suicidal thoughts and attempted suicide. The manufacturer was instructed by the US FDA to conduct a large randomised control trial of over 8,000 people to look specifically at this issue. The results were published in 2016 and did not show an increase in mental health symptoms in people on any of the treatments for smoking cessation, including varenicline. The European Medicines and Healthcare products Regulatory Agency (MHRA) and the FDA have now removed their warnings regarding varenicline and behavioural or mood changes. The FDA states: "The results of the trial confirm that the benefits of stopping smoking outweigh the risks of these medicines."

Varenicline is generally thought to be a safe medicine for most people. However, it is a relatively new medicine and so caution is used in certain people. For example, it is not licensed to be used in people who are pregnant or breastfeeding, those under the age of 18 years, and those with severe kidney failure. Your doctor or practice nurse will advise if you are suitable for this medicine. If you are unable to take varenicline, there are other ways that you can get help to quit. See the separate leaflet called Quit Smoking (Smoking Cessation).

How to use the Yellow Card Scheme

If you think you have had a side-effect to one of your medicines you can report this on the Yellow Card Scheme. You can do this online at

The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that medicines or any other healthcare products may have caused. If you wish to report a side-effect, you will need to provide basic information about:

  • The side-effect.
  • The name of the medicine which you think caused it.
  • The person who had the side-effect.
  • Your contact details as the reporter of the side-effect.

It is helpful if you have your medication - and/or the leaflet that came with it - with you while you fill out the report.

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Further reading and references