Varenicline tartrate is an orally active, subtype-selective partial agonist at alpha4 beta2 nicotinic receptors with Ki values of 0.06, 240, 322 and 3540 nM for alpha4 beta2, alpha3 beta4, alpha7, alpha1 beta gamma delta receptors respectively, and a full agonist at alpha7 neuronal nicotinic receptors. In humans, following oral administration, varenicline is almost completely absorbed and has high bioavailability (90%). Varenicline stimulates basal mesolimbic dopamine release to approximately 50% of the maximal effect of nicotine, inhibits nicotine-induced dopamine release, and reduces nicotine self-administration. Varenicline is a clinically useful smoking cessation agent.
