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: Clinical evaluation of adverse effects during bepridil administration for atrial fibrillation and flutter .
### Output Text:
Clinical evaluation of adverse effects during <span class="chemical">bepridil</span> administration for atrial fibrillation and flutter . 