In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: METHODS : Three groups were established : a control group ( n = 10 ) , a high - dose group ( n = 10 ) , treated with one intraperitoneal injection of indomethacin 20 mg / kg , and a therapeutic dose group ( n = 10 ) in which oral indomethacin was administered 3 . 25 mg / kg body weight daily for 3 weeks .
### Output Text:
METHODS : Three groups were established : a control group ( n = 10 ) , a high - dose group ( n = 10 ) , treated with one intraperitoneal injection of <span class="chemical">indomethacin</span> 20 mg / kg , and a therapeutic dose group ( n = 10 ) in which oral <span class="chemical">indomethacin</span> was administered 3 . 25 mg / kg body weight daily for 3 weeks . 