Cytisine is an alkaloid found in plants of the Fabaceae family (the pea family) and it competes with nicotinic receptors. When something actively competes for a receptor then it has a very gentle effect at the site and effectively helps to alleviate cravings.
Cytisine is very cheap and just as effective as other nicotine replacements such as NRT patches and gum. The cost is about $30 a month compared to other treatments that can be as expensive as $300 a month. It's not a new therapy, having been used in Eastern Europe for a long time, but for some reason has remained relatively unknown outside of this area.
For further information you can read the following research: http://www.nejm.org/doi/full/10.1056/NEJMoa1407764
Yours in health