388
PK and PD studies in Sprague - Dawley rats revealed that the bioavailability of the drug using optimal SD was about twofold higher than that of reference product , and the irritation area of stomach was significantly reduced in the ulcer - induced rat model using optimal SD as compared to the reference product .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 None