Varenicline: mode of action, efficacy, safety and accumulated experience salient for clinical populations.

Varenicline, a selective partial agonist of the α4β2 nicotinic acetylcholine receptor, is a smoking cessation pharmacotherapy that more than doubles the chance of quitting smoking at 6 months compared with placebo. This article reviews salient knowledge of the discovery, pharmacological characteristics, and the efficacy and safety of varenicline in general and in specific populations of smokers and provides recommendations to support use in clinical practice.: Literature searches for varenicline were conducted using PubMed, with date limitations of 2000-2018 inclusive, using search terms covering the discovery, mechanism of action, pharmacokinetics, efficacy and safety in different populations of smokers, alternative quit approaches and combination therapy. Selection of safety and efficacy data was limited to clinical trials, meta-analyses and observational studies. Standard administration of varenicline is efficacious in helping smokers to quit, including smokers with cardiovascular disease and chronic obstructive pulmonary disease. Furthermore, varenicline efficacy may be improved with pre-loading, a gradual quitting approach for smokers unwilling or unable to quit abruptly, and extended treatment in smokers who have recently quit to help maintain abstinence. Initial concerns regarding the association of varenicline with increased risk of neuropsychiatric and cardiovascular adverse events have been disproven after extensive clinical evaluations, and the benefit-risk profile of varenicline is considered favorable. Varenicline is efficacious and safe for all adult smokers with a range of clinical characteristics. Evidence suggests that approaches offering greater flexibility in timing and duration of treatment may further extend treatment efficacy and clinical reach.