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: The authors present a case of early ( within 4 days ) development of torsade de pointes ( TdP ) associated with oral amiodarone therapy .
### Output Text:
The authors present a case of early ( within 4 days ) development of torsade de pointes ( TdP ) associated with oral <span class="chemical">amiodarone</span> therapy . 