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: Careful fluid administration and cautious use of titrated doses of ephedrine are advised .
### Output Text:
Careful fluid administration and cautious use of titrated doses of <span class="chemical">ephedrine</span> are advised . 