A method for decreasing nicotine and other substance use in humans is disclosed. Iptakalim hydrochloride (IPT) is a novel nicotine acetylcholine receptor (nAChR) blocker. According to the disclosed method, IPT is used to block human α4β2-nAChR function. Specifically, IPT exhibits a selective blockade of α4 subunit-containing human nAChR subtypes. According to the disclosed method, IPT is thus used to block the major nicotine targets in the brain, the α4β2-nAChRs natively expressed in midbrain (VTA) DA system, the brain reward center, and in turn to reduce the nicotine-induced reward signals, namely dopamine level increase in nucleus accumbens. Therefore, IPT is capable of servicing as a nAChR antagonist agent and thus is a novel treatment for decreasing nicotine dependence in humans.