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: Based on nonoverdose pharmacokinetics and pharmacodynamics of venlafaxine and the potential risks of available interventions , no emergent therapy was instituted .
### Output Text:
Based on nonoverdose pharmacokinetics and pharmacodynamics of <span class="chemical">venlafaxine</span> and the potential risks of available interventions , no emergent therapy was instituted . 