2809
The degree and time course of development of tolerance to daily administration of sub - effective dose combinations of ketamine and morphine were similar .
 Chemical: ketamine; Chemical: morphine
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: ketamine; Chemical: morphine