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: MESNA was given orally on the days of treatment with IF in 3 doses of 840 mg / m2 , each administered at 0 hr ( = injection of IF ) , 4 hr and 8 hr p . i .
### Output Text:
<span class="chemical">MESNA</span> was given orally on the days of treatment with <span class="chemical">IF</span> in 3 doses of 840 mg / m2 , each administered at 0 hr ( = injection of <span class="chemical">IF</span> ) , 4 hr and 8 hr p . i . 