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Ketamine is primarily metabolized to norketamine by hepatic cytochrome P450 ( CYP ) 2B6 and CYP3A4 - mediated N - demethylation .
 Ketamine, norketamine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Ketamine, norketamine