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: Both patients were treated preoperatively with beta - adrenergic antagonist medications , which may have masked the cardiovascular signs of the unintentional intravascular administration of levobupivacaine with epinephrine .
### Output Text:
Both patients were treated preoperatively with beta - adrenergic antagonist medications , which may have masked the cardiovascular signs of the unintentional intravascular administration of <span class="chemical">levobupivacaine</span> with <span class="chemical">epinephrine</span> . 