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: RESULTS : Maternal toxicity , intrauterine growth retardation , and increase of external and skeletal variations were found in rats treated with the highest dose of piroxicam .
### Output Text:
RESULTS : Maternal toxicity , intrauterine growth retardation , and increase of external and skeletal variations were found in rats treated with the highest dose of <span class="chemical">piroxicam</span> . 