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: However , when the dose is adjusted based on clinical response or the development of adverse effects , 75 % of patients with VT or VF can be successfully managed with amiodarone .
### Output Text:
However , when the dose is adjusted based on clinical response or the development of adverse effects , 75 % of patients with VT or VF can be successfully managed with <span class="chemical">amiodarone</span> . 