α4β2 nicotinic partial agonist Pregnancy: As a precautionary measure, preferable to avoid use during pregnancy. Breast-feeding: unknown whether excreted in human milk (animal data suggest excretion) - weigh benefit of breast-feeding against benefit of therapy.

Varenicline

Brand names: Champix

Varenicline is an oral nicotinic-receptor partial agonist used as an aid to smoking cessation. It reduces cravings and lessens the reward and satisfaction obtained from smoking.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 1 mg

Route: Oral

Frequency: Twice daily (after a 1-week titration)

Max: 1 mg twice daily

Titration: Days 1-3: 0.5 mg once daily; Days 4-7: 0.5 mg twice daily; Day 8 to end of treatment: 1 mg twice daily. Patient should set a quit date and usually start varenicline 1-2 weeks before it. Treat for 12 weeks; for those who have stopped smoking at 12 weeks, an additional 12-week course at 1 mg twice daily may be considered to maintain abstinence. Gradual approach for those unable/unwilling to quit abruptly: reduce smoking during the first 12 weeks and quit by the end, then continue for a further 12 weeks (total 24 weeks). Patients who cannot tolerate adverse reactions may have the dose lowered temporarily or permanently to 0.5 mg twice daily. Swallow tablets whole with water; may be taken with or without food. Not recommended in paediatric patients - efficacy not demonstrated.

Dose adjustments

Renal

No adjustment for mild to moderate renal impairment. Moderate impairment with intolerable adverse reactions: may reduce to 1 mg once daily. Severe renal impairment (estimated CrCl <30 ml/min): recommended dose 1 mg once daily, beginning 0.5 mg once daily for the first 3 days then increasing to 1 mg once daily. End-stage renal disease: treatment not recommended (UK SPC).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

Begin varenicline tablets dosing one week before the date set by the patient to stop smoking. Alternatively, the patient can begin varenicline tablets dosing and then quit smoking between days 8 and 35 of treatment. ( 2.1 ) Starting Week: 0.5 mg once daily on days 1 to 3 and 0.5 mg twice daily on days 4 to 7. ( 2.1 ) Continuing Weeks: 1 mg twice daily for a total of 12 weeks. ( 2.1 ) An additional 12 weeks of treatment is recommended for successful quitters to increase likelihood of long-term abstinence. ( 2.1 ) Consider a gradual approach to quitting smoking with varenicline tablets for patients who are sure that they are not able or willing to quit abruptly. Patients should begin …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-05-08. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hypersensitivity to varenicline or to any excipient

Side effects

Nausea (very common, ~28.6%; usually early, mild to moderate)
Abnormal dreams and insomnia (very common)
Headache (very common)
Nasopharyngitis (very common)
Somnolence, dizziness, dysgeusia (common); neuropsychiatric symptoms including mood changes and suicidal ideation reported (discontinue and seek review)

Interactions

Smoking cessation (with or without varenicline) may alter the pharmacokinetics/pharmacodynamics of CYP1A2 substrates - e.g. theophylline, warfarin, insulin - dose adjustment may be needed
Nicotine replacement therapy - increased incidence of nausea, headache, vomiting, dizziness, dyspepsia and fatigue when combined
Alcohol - increased effects of alcohol reported (US labelling)

Clinical monograph

How it works

It binds partially to alpha-4-beta-2 nicotinic acetylcholine receptors, providing enough stimulation to relieve withdrawal while blocking nicotine from those receptors, so smoking becomes less rewarding.

Prescribing in practice

Monitor mood and behaviour, and advise the person to report low mood, agitation, unusual behaviour or suicidal thoughts.
Treatment is started before the planned quit date, with the dose titrated up over the first week.
Nausea is common, along with abnormal or vivid dreams, insomnia, headache and constipation; dose reduction may help if side effects are troublesome.

Monitoring

Monitor mood, behaviour and smoking status during treatment, with particular attention to any new or worsening psychiatric symptoms.

Counselling the patient

Start the medicine before your quit date and set a date to stop smoking as advised.
Take it after food with a full glass of water to reduce nausea.
Tell someone and seek advice promptly if you notice low mood, agitation or thoughts of self-harm.

Evidence & guidelines

Recommended for smoking cessation by NICE (NG209).

Reference: NICE NG209; MHRA; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways