• Pregnancy and breastfeeding: varenicline should not be used during pregnancy or breastfeeding.
• Children and adolescents: varenicline is not licensed for use in smokers younger than 18 years of age.
• Epilepsy: there is no clinical experience of varenicline in people with epilepsy.
• Renal impairment:
• Mild-to-moderate renal impairment: no dosage adjustment necessary.
• Severe renal impairment (estimated creatinine clearance < 30 mL/min): the recommended dose is varenicline 1 mg once daily. Start treatment with a dose of 500 micrograms once a day for the first 3 days, then increase to 1 mg once a day.
• Varenicline is not recommended for people who have end-stage renal disease.

In depth

• The recommended treatment dose is 1 mg varenicline twice daily following a 1-week titration as follows:
• Days 1–3: 500 micrograms once a day.
• Days 4–7: 500 micrograms twice a day.
• Day 8 onwards: 1 mg twice a day.
• For people who cannot tolerate the adverse effects of higher doses (1 mg twice daily) of varenicline, the dose may be reduced to 0.5 mg twice a day.
• Advise the person to stop smoking 7–14 days after starting varenicline.
• The recommended course of treatment is 12 weeks.
• For people who have successfully stopped smoking at the end of 12 weeks, an additional course of 12 weeks' treatment with varenicline at 1 mg twice daily may be considered to help maintain abstinence.
• Varenicline may be stopped without tapering the dose. However, immediately after stopping treatment with varenicline, up to 3% of people experience an increase in irritability, urge to smoke, depression, or insomnia. Inform the person accordingly and discuss or consider the need for dose tapering.

In depth

• The most common adverse effect is mild-to-moderate nausea, which usually occurs early in the treatment period.
• Other common adverse effects include headache, insomnia, abnormal dreams, increased appetite, somnolence, dizziness, vomiting, constipation, diarrhoea, abdominal distension and discomfort, dyspepsia, flatulence, dry mouth, and fatigue.
• Varenicline may cause dizziness and somnolence, and therefore may influence the ability to drive and use machines. Advise the person not to drive, operate complex machinery, or engage in other potentially hazardous activities until it is known whether varenicline affects their ability to perform these activities.
• There have been reports of depression and suicidal ideation associated with the use of varenicline. Prescribers are advised that:
• Patients should be told to stop treatment and contact their doctor immediately if they develop suicidal thoughts or behaviour.
• Varenicline should be stopped immediately if agitation, depressed mood, or changes in behaviour are observed that are of concern to the patient, family, or caregivers.
• The safety and efficacy of varenicline in people with serious psychiatric illness have not been established. Patients who have a history of psychiatric illness should be monitored closely while taking varenicline.

In depth