20011
METHODS : Overnight - deprived smokers ( n = 24 ) and nonsmokers ( n = 20 ) completed six neuroimaging assessments on different days both in the absence of , and following , varenicline and / or nicotine administration .
 Chemical: varenicline; Chemical: nicotine
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: varenicline; Chemical: nicotine