3707
The brain concentration of NA was not changed by morphine and fentanyl , but one of the doses of codeine ( 45 mg / kg ) slightly enhanced it .
 Chemical: NA; Chemical: morphine; Chemical: fentanyl; Chemical: codeine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: NA; Chemical: morphine; Chemical: fentanyl; Chemical: codeine