Varenicline is a partial agonist/antagonist of α4β2 nicotinic acetylcholine receptor [1].
Varenicline is a manufactured tartrate salt, it is a partial agonist of α4β2 nAChRs. The affinity(0.15 nM) of varenicline with α4β2 nAChRs is much more higher than with other nAChR subtypes. Through the binding, varenicline prevents nicotine from occupying the receptors and subsequently inhibit nicotine-induced dopaminergic activation. So varenicline is used for smoking cessation. In healthy adult smokers, varenicline does not undergo significant hepatic metabolism and the clearance(>90%) is predominantly renal. It is shown that the amphetamine administration may have decrease the efficacy of varenicline [1].
References:
[1] Garrison GD, Dugan SE. Varenicline: a first-line treatment option for smoking cessation. Clin Ther. 2009 Mar;31(3):463-91.