Varenicline

Key facts

• Varenicline is a smoking-cessation medicine that partially activates the brain's nicotine receptors, reducing cravings and withdrawal symptoms and making cigarettes less rewarding if you do smoke.
• You usually start it while still smoking, choose a quit date within the first one to two weeks, and continue treatment for about twelve weeks.
• Varenicline can cause mood and behaviour changes, including agitation, low mood and, rarely, thoughts of self-harm. Vivid or unusual dreams are also common. Tell your prescriber promptly about any new mood changes, and be cautious with driving or operating machinery until you know how it affects you.
• Seek urgent care for thoughts of self-harm, severe mood changes, chest pain, or signs of an allergic reaction such as rash, swelling or breathing difficulty.

What varenicline treats

Varenicline helps adults stop smoking. It's used as part of a quit-smoking plan, usually alongside behavioural support and counselling, to reduce cravings and withdrawal symptoms during the quit attempt.

How varenicline works

Nicotine works by activating receptors in the brain that trigger the release of dopamine, producing the pleasurable effects of smoking. Varenicline attaches to the same receptors but activates them only partially, easing craving and withdrawal on its own while also blocking nicotine from binding fully if you smoke, which blunts the reward.

Before you take it

• Tell your prescriber about any history of depression, other mental health conditions, or seizures before starting.
• Mention significant kidney impairment, since the dose may need adjusting.
• Tell your prescriber about heart disease, since cardiovascular events have been reported during treatment.
• Alcohol can increase mood-related side effects, so limit your intake while on treatment.

Side effects

Common effects include nausea, sleep disturbance or vivid dreams, headache, and constipation.

Stop and seek urgent medical care for any of these:

• New or worsening depression, agitation, or thoughts of self-harm.
• Severe allergic reaction with rash, swelling, or difficulty breathing.
• Chest pain or an unusual, rapid heartbeat.
• A seizure.

Safety essentials

• Watch for and report any new depression, agitation, or thoughts of self-harm, especially in the first weeks or if you have a history of mental illness. Ask family or friends to watch for changes too.
• Vivid dreams and occasional dizziness can affect alertness, so be cautious driving or using machinery until you know how varenicline affects you.
• Limit alcohol, which can worsen mood side effects, and make sure your prescriber knows about any history of seizures before you start.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.