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: An adverse drug interaction with piroxicam , which she took occasionally , may have exacerbated the coagulopathy .
### Output Text:
An adverse drug interaction with <span class="chemical">piroxicam</span> , which she took occasionally , may have exacerbated the coagulopathy . 