1310 adult daily smokers who were motivated to quit received cytisine tablets (1/5 mg/tablet) for 25 days according to the manufacturers recommended protocol: days 1 through 3, one tablet every 2 hours through the waking day (up to six tablets per day); days 4 through 12, one tablet every 2.5 hours (up to five tablets per day); days 13 through 16, one tablet every 3 hours (up to four tablets per day); days 17 through 20, one tablet every 4 to 5 hours (three tablets per day); and days 21 through 25, one tablet every 6 hours (two tablets per day). When combined with brief behavioral support, cytisine was found to be superior to nicotine-replacement therapy in helping smokers quit smoking, but it was associated with a higher frequency of self-reported adverse events.

The parenteral cell line tsA201 (derived from embryonic kidney HEK-293 cells) was transfected with Human α3, α4, α7, β2 and β4 nicotinic acetylcholine receptor DNA. Transfected cells stably expressing α4β2 AChRs were grown in Dulbecco's modified Eagle's medium with 10% fetal bovine serum supplemented with 2 mM glutamine and incubated at 37 deg C in a 5% CO2 atmosphere. Cells were plated in a 96-well plate and incubated for 48 hours prior to assaying against various nicotinic agonists, including Cytisine. To measure responses to various nicotinic agonists, 100 µl of a fluorescent dye which is sensitive to changes in membrane potential was added to the wells with the addition of 0.5 microM atropine to block muscarinic responses. The plates were then incubated for 1 hour at 37 deg-C. Serial dilutions of Cytisine were prepared in Hanks Balanced Salt Solution and added to the appropriate well after 20 seconds and fluorescence response monitored for 60 - 120 seconds using a FLEX Station at 25°C. The EC50 of Cytisine was found to be 5.5 micro M against α4β2 AChRs.