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: This side effect of IFO raises the requirement for the co - administration with sodium 2 - sulfanylethanesulfonate ( Mesna ) aiming to avoid or minimize this effect .
### Output Text:
This side effect of <span class="chemical">IFO</span> raises the requirement for the co - administration with <span class="chemical">sodium 2 - sulfanylethanesulfonate</span> ( <span class="chemical">Mesna</span> ) aiming to avoid or minimize this effect . 