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: CONCLUSIONS : This study suggests that the use of amiodarone in elderly patients with AF and a previous MI increases the risk of bradyarrhythmia requiring a permanent pacemaker .
### Output Text:
CONCLUSIONS : This study suggests that the use of <span class="chemical">amiodarone</span> in elderly patients with AF and a previous MI increases the risk of bradyarrhythmia requiring a permanent pacemaker . 