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: Ototoxicity appeared closely related to a prolonged administration and higher total dose of ototoxic drugs , particularly aminoglycosides and furosemide .
### Output Text:
Ototoxicity appeared closely related to a prolonged administration and higher total dose of ototoxic drugs , particularly <span class="chemical">aminoglycosides</span> and <span class="chemical">furosemide</span> . 