Pharmacology · Smoking cessation medicines
Varenicline !
A nicotinic receptor partial agonist that eases craving and makes smoking less rewarding. Nausea and vivid dreams are common.
Updated 2026-11-01
The figure shows varenicline itself bound to the human α4β2 nicotinic acetylcholine receptor.
Mechanism of action
Varenicline, designed from cytisine, binds α4β2 nicotinic receptors as a partial agonist. It stimulates them enough to ease craving and withdrawal, while occupying the site so nicotine from a cigarette binds less and drives less mesolimbic dopamine reward.
- Binds α4β2 nicotinic receptors as a partial agonist
- Partial stimulation eases craving and withdrawal
- Nicotine is blocked: smoking rewards less
Pharmacokinetics
- Metabolism
- Minimal
- Elimination
- Mainly in the urine, about 92% unchanged
- Half-life
- About 24 hours
Indications
- Aid to smoking cessation Tobacco use disorder →
Adverse effects
Common
- Nausea (the most common)
- Abnormal dreams and insomnia
- Constipation, flatulence and vomiting
Contraindications
- Serious hypersensitivity or skin reaction to varenicline
Key interactions
- Nicotine patch
- More adverse effects than nicotine replacement alone
- Alcohol
- Stronger intoxication; alcohol intake is reduced
- Theophylline, warfarin, insulin (effect of quitting smoking)
- Their effects may change after stopping smoking; doses may need review
What is monitored
- Mood, behaviour and suicidal thoughts
- Kidney function
- Smoking status and adherence
Administration and safety
- Given by mouth after food with a full glass of water
- Usually started one week before the chosen quit date
- Dose adjusted in severe kidney impairment
Nursing care
- Ask about mental health history before starting
- Teach to report mood changes, agitation or suicidal thoughts at once
- Teach to be careful driving until the effect is known and to cut down alcohol
- Offer counselling alongside the medicine
Pregnancy and breastfeeding
Available data have not shown more major birth defects than in women who smoke, but a risk cannot be ruled out.
Test yourself
Think of the answer, then tap the question to see it.
How does varenicline make smoking less rewarding?
As a partial agonist it occupies α4β2 receptors and blocks nicotine from binding.
When is varenicline usually started relative to the quit date?
About one week before the chosen quit date.
Why is the varenicline dose adjusted in severe kidney disease?
About 92% is excreted unchanged in the urine.
What is the most common adverse effect of varenicline?
Nausea.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - VARENICLINE tablet, film coated VARENICLINE kit (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 13 (McGraw Hill, 2023); 6UR8: CryoEM structure of human alpha4beta2 nicotinic acetylcholine receptor in complex with varenicline (RCSB Protein Data Bank, 2020).
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Representative model, for educational purposes only.