Varenicline-15N3 Hydrochloride (CP 526555-15N3 Hydrochloride) is the 15 N labeled isotope of Varenicline hydrochloride. Varenicline (CP 526555) is an orally active partial agonist of α4β2 nicotinic acetylcholine receptor (α4β2 nAChR , IC 50 = 250 nM), which is the principal mediator of nicotine dependence. Varenicline is also a partial agonist of α6β2 nAChR and a full agonist of α6β2 nAChR. Varenicline blocks the direct agonist effects of nicotine on nAChR while stimulates nAChR in a more moderate way, being widely used as an aid of smoking cessation.