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: Protection with oral MESNA is particularly suitable for outpatients .
### Output Text:
Protection with oral <span class="chemical">MESNA</span> is particularly suitable for outpatients . 