18797
PURPOSE : Omeprazole has ( R ) - and ( S ) - enantiomers , which exhibit different pharmacokinetics ( PK ) among patients with cytochrome P450 ( CYP ) 2C19 genotype groups .
 Omeprazole
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Omeprazole