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 speculate that the increased vagal tone during bladder irrigation , a vagal maneuver , in the context of amiodarone therapy resulted in amiodarone - induced proarrhythmia .
### Output Text:
The authors speculate that the increased vagal tone during bladder irrigation , a vagal maneuver , in the context of <span class="chemical">amiodarone</span> therapy resulted in <span class="chemical">amiodarone</span> - induced proarrhythmia . 