The most recent non-nicotine medication is Varenicline (Chantix), a partial agonist selective for a specific nicotine receptor subtype, was approved in 2006.  The drug’s efficacy is believed to be the result of a sustained, low-level agonist activity at the receptor site, combined with competitive blockade of nicotine binding.  The partial agonist activity modestly stimulates receptors, leading to increased dopamine levels that reduce nicotine withdrawal symptoms.  By blocking the binding of nicotine to receptors in the central nervous system, Varenicline inhibits the surge of dopamine release that occurs immediately (7 to 10 seconds) following each inhalation of tobacco smoke.  This effect may help prevent relapse by reducing or even eliminating the pleasure linked with smoking.  Evidence suggests that using Varenicline can increase successful quitting 3 times more when compared to placebo.