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: To our knowledge and after reviewing the literature there is one case report of myxedema coma during long term amiodarone therapy .
### Output Text:
To our knowledge and after reviewing the literature there is one case report of myxedema coma during long term <span class="chemical">amiodarone</span> therapy . 