21572
CONCLUSIONS : These results suggest that differences in pharmacologic mechanism between nicotine , varenicline , and cytisine include not only differences in efficacy at a common subtype of nicotinic acetylcholine receptor , but also differential affinity and / or efficacy at multiple receptor subtypes .
 Chemical: nicotine; Chemical: varenicline; Chemical: cytisine; Chemical: acetylcholine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: nicotine; Chemical: varenicline; Chemical: cytisine; Chemical: acetylcholine