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: This is a case report of myxedema coma secondary to amiodarone - induced hypothyroidism in a patient with severe congestive heart failure ( CHF ) .
### Output Text:
This is a case report of myxedema coma secondary to <span class="chemical">amiodarone</span> - induced hypothyroidism in a patient with severe congestive heart failure ( CHF ) . 