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: Electrophysiologic and hemodynamic effects of flestolol are similar to those of other beta blockers .
### Output Text:
Electrophysiologic and hemodynamic effects of <span class="chemical">flestolol</span> are similar to those of other beta blockers . 