12304
In vitro studies were performed in the absence of S9 metabolic activation using blood from five healthy volunteers , incubated 72 h with isotretinoin ( 1 . 2 - 20 mu M ) ( i . e . , at concentrations usually achieved in blood with therapeutic doses as well as at higher concentrations ) .
 isotretinoin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 isotretinoin