16668
Since fed state conditions cannot easily be implemented in the presently available permeability tools , including the frequently used Caco - 2 system , exploring food effects during drug development can be quite challenging .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None