Champix® is a medicine that was first licensed in the UK in December 2006. It was developed to help smokers to stop smoking. Champix contains the active ingredient Varenicline which mimics the effect of nicotine on the body. Therefore, it both reduces the urge to smoke and relieves withdrawal symptoms.
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Nicotine is a drug that is inhaled from the tobacco in cigarettes. It gets into the bloodstream, and stimulates the brain. Most regular smokers are addicted to nicotine. About 2 in 3 smokers want to stop smoking but, without help, many fail to succeed. The main reason why so few smokers succeed, even though they want to stop smoking, is because nicotine addiction is strong and difficult to break. This is where varenicline can help.

What is varenicline and how does it work?


How effective is varenicline?


How do I take varenicline?


  • 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 gets 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.
  • Tell your doctor if you develop any side-effects. A reduction in dose may be an option if the side-effect is not serious.


  • 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.


Are there any possible side-effects?

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.

Common but not usually serious side-effects

The most commonly reported side-effect is nausea (feeling sick). 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: insomnia (difficulty sleeping), abnormal dreams, headaches and flatulence (wind). Taking the evening dose after your evening meal, and not just before bedtime, is thought to reduce any sleep-related side-effects.

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 vascular disease.) The warning was based on a research study that followed 700 smokers with cardiovascular disease who were treated with varenicline or placebo (dummy tablets). The results of the study confirmed that varenicline was effective in helping people to quit smoking. Also, that adverse cardiovascular events 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.) Therefore, the FDA has said it will continue to monitor the situation and has asked the manufacturer to provide more information on the data they hold. In the meantime, they advise people who take varenicline to report to their doctor any new or worsening symptoms of cardiovascular disease. For example: shortness of breath or trouble breathing; new or worsening chest pain; new or worse pain in the legs when walking.

A possible increase in mood and behavioural changes

Since it has been introduced, there have been various reports of a possible link between varenicline and behavioural or mood changes. The suspected symptoms include hostility, agitation, depressed mood, suicidal thoughts and attempted suicide. There is no proof that these symptoms are any more common in people taking varenicline compared with the general population. Also, a study published in 2009 was reassuring in that it didn’t find any link between varenicline and depression or suicidal thoughts. However, it concluded that a small increased risk of self-harm with varenicline could not be definitely ruled out. So, to play safe, if you take varenicline, you should get in touch with your doctor if you experience any behavioural or mood changes.

Who should not take varenicline?

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 breast-feeding, those under the age of 18, and those with severe kidney failure. It may also be used with more caution in people who have certain conditions, such as certain mental health disorders. Also, the possible concerns about heart problems and mood and behaviour are discussed above. Your doctor or practice nurse will advise if you are suitable for this medicine.