Varenicline (Champix®)

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

Nicotine is a substance that is inhaled from the tobacco in cigarettes. It gets into the bloodstream, and stimulates the brain. Most regular smokers are addicted to nicotine.

If you are a smoker, when the blood level of nicotine falls, you usually develop withdrawal symptoms such as restlessness, increased appetite, inability to concentrate, irritability, dizziness, constipation, nicotine craving, or just feeling awful. These symptoms begin within a few hours after having the last cigarette. If they are not relieved by the next cigarette, withdrawal symptoms become worse. If you do not smoke any more cigarettes, the withdrawal symptoms peak after about 24 hours, and then gradually ease over about 2-4 weeks. So, most smokers smoke regularly to prevent withdrawal symptoms.

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.

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Varenicline (Champix®) is a medicine that was first licensed in the UK in December 2006. It 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, it 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.

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 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.
  • Take each dose 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 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.

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 or use machines. You should not drive or 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 vascular 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 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.

Regarding this point, the Medicines and Healthcare products Regulatory Agency (MHRA) states: "People who are taking varenicline who develop suicidal thoughts, agitation, depressed mood, or display any changes in behaviour or thinking that are of concern for the doctor, patient, family, or caregiver should stop varenicline and contact their doctor immediately."

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 following web address:

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.

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.

Original Author:
Dr Tim Kenny
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
4903 (v43)
Last Checked:
Next Review:
The Information Standard - certified member
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