How effective are nicotine receptor partial agonists for smoking cessation?
Two open-label trials of varenicline versus NRT suggested a modest benefit for varenicline, but were inconclusive. Possible links with serious adverse events, including depressed mood, agitation and suicidal thoughts, have been reported but are so far not substantiated. Cytisine may also increase the chances of quitting, but the evidence at present is inconclusive.
Varenicline was developed as a nicotine receptor partial agonist from cytisine, a drug widely used in central and eastern Europe for smoking cessation. Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine, to counteract withdrawal symptoms (acting as an agonist), and reducing smoking satisfaction (acting as an antagonist).