Champix Side Effects: What the Canadian Label Lists

The Champix label does not treat every side effect the same way. The product monograph, a document written for health professionals, sorts them into effects seen in the trials before approval, effects reported by patients after the drug was on the market, and a short list of warnings that tell you when to stop the tablets. This page uses the March 2018 monograph and leaves out who can take the drug and how it works, which our Champix and varenicline page covers. Nothing here is personal medical advice.

What did the trials find?

The monograph says that in the trials before approval, adverse events began in the first few weeks of therapy and were generally mild to moderate. It describes the nausea as often transient, though for some people it lasted the whole treatment.

In 12-week placebo-controlled studies at the higher dose, 12% of people taking Champix stopped because of adverse events, compared with 10% on placebo. The reasons that came up most often were nausea (2.7% against 0.6% on placebo), insomnia (1.3% against 1.2%), fatigue, malaise or weakness (1.0% against 0.5%) and dizziness (0.7% against 0.4%).

The monograph also notes that quitting smoking, with or without a medicine, brings low mood, trouble sleeping, irritability and anxiety, so some symptoms may come from withdrawal. Our page on nicotine withdrawal symptoms covers that list.

Which side effects does the patient leaflet name?

The consumer leaflet, which is part III of the monograph, lists these as some of the most common side effects:

• nausea and vomiting
• trouble sleeping
• headache
• abnormal dreams
• sleepiness, tiredness and dizziness
• constipation, diarrhea and gas

It says these are mostly mild to moderate and usually occur in the first weeks of treatment. The leaflet also says to avoid driving or dangerous machines until you know how Champix affects you, because some people reported sleepiness, dizziness or blackouts.

Which reactions does the label treat as serious?

The leaflet gives specific instructions for several of them.

Mood and behaviour. People have reported changes in behaviour or thinking, hostility, agitation, aggression, depressed mood and suicidal thoughts or actions, both in people with and without earlier mental health problems. The leaflet says that if your thoughts, moods or behaviours are severe, concerning or very abnormal for you, you should stop taking Champix right away, seek medical help and tell your healthcare provider. It adds that in many people the symptoms went away after stopping, but not in all. The post-approval list also includes anxiety, mania, hallucinations and paranoia, and the monograph says those reports come from a population of uncertain size, so frequency cannot be reliably estimated.

Allergic reactions. The leaflet describes swelling of the face, mouth and throat that can cause trouble breathing. For a rash with peeling skin or blisters in the mouth, around the eyes or on the genitals, it says to stop taking Champix and seek immediate emergency medical attention. The monograph names angioedema, Stevens-Johnson syndrome and erythema multiforme among the post-approval reports.

Heart and stroke events. New or worse heart or blood vessel problems have been reported, mainly in people who already had them. The leaflet says it is not possible to determine whether Champix increases the risk of heart or stroke events, and it lists warning signs that need emergency help.

Sleepwalking. The leaflet says it has been reported and may sometimes lead to harmful behaviour. It says to stop taking Champix and tell your healthcare provider.

Alcohol. The leaflet says drinking may raise the risk of mental health symptoms. Reported experiences include aggressive behaviour, feeling more intoxicated than expected and no memory of events.

Blood sugar. People with diabetes may need to check their blood sugar more often, and the monograph mentions reports of new-onset diabetes in some people without it.

What about the 2021 recall?

In June 2021, Health Canada posted a Type II recall of a Champix 0.5 mg tablet lot and several lots of the 0.5 mg and 1.0 mg tablet kit. The reason was an impurity, N-nitrosovarenicline, above the acceptable limit. A Health Canada letter later that month said the impurity may be associated with a potential increased cancer risk in humans, but that there was no immediate risk to patients, because any increased risk would be tied to long-term use. It told patients to continue taking the medicine as prescribed. It concerned specific lots, so ask a pharmacist about the product you are given.

How do you report a side effect?

Health Canada says anyone can report a side effect to a health product, and that you should do so as soon as possible, even if you are not sure the product caused it. The monograph leaflet gives the Canada Vigilance Program toll-free line, 1-866-234-2345, and says the program does not provide medical advice. For advice on a symptom, call your pharmacist or doctor.

Health Canada also says the Canada Vigilance database should not be used on its own to judge a product’s safety, since the reports are submitted voluntarily.

Where can you get help deciding?

A doctor or pharmacist can go through your history and other medicines. If side effects make Champix a poor fit, see the overview of quit-smoking medications and ask whether your pharmacy has a cessation program. Stopping and trying again is common; see how many tries it takes. If you are pregnant, read quitting smoking while pregnant first.

What we could not confirm

• Current side-effect wording. We read the March 2018 monograph; the Drug Product Database lists a later one that we did not open.
• Frequencies for most side effects. The trial table in the PDF did not read cleanly, so we give figures only for nausea, stopping rates and the four reasons named above.
• How often serious reactions happen. The label does not give a rate for post-approval reports.
• The current status of the 2021 recall.