Cytisine is a partial nicotine agonist extracted from acacia seeds. In a single-center trial, West et al randomized 740 smokers to receive either cytisine or placebo for 25 days; they were then followed for 12 months with surveys and periodic biochemical verification.
At 12 months, those receiving cytisine had an 8.4% rate of biochemically verified smoking abstinence, compared with 2.4% in the placebo group. The cytisine users did report more gastrointestinal side effects (5.7% more reporting stomach pain, dyspepsia, nausea, or dry mouth).
Since cytisine only costs $15 for a treatment course, it could become a great option for low-income people who want to quit (who make up a disporportionate amount of smokers, and are less likely to be insured or able to afford pharmaceutical smoking cessation aids).
West R et al. Placebo-Controlled Trial of Cytisine for Smoking Cessation. N Eng J Med 2011; 365:1193-1200.