18800
Blood samples were drawn 4 h after the intake of an oral dose of omeprazole 40 mg , and plasma levels of omeprazole and its metabolites were analyzed by high - performance liquid chromatography ( HPLC ) using a chiral column .
 omeprazole, omeprazole
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 omeprazole, omeprazole