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: Addition of misoprostol can minimize this renal impairment without affecting pain control .
### Output Text:
Addition of <span class="chemical">misoprostol</span> can minimize this renal impairment without affecting pain control . 