There are no clinical trials investigating the efficacy of cytisine in AD, although two clinical studies explored the effect of cytisine on the biochemistry of AD, which reached the conclusion that selective nicotinic receptor agonists, such as cytisine, not only reduce Aβ levels but may also protect against nAChR loss in the Alzheimer’s brain [82, 83]. This evidence concerns the gene CHRNA4 and Alzheimer disease.