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: She was admitted to the medical intensive care unit , venlafaxine was discontinued , and no further sequelae were seen .
### Output Text:
She was admitted to the medical intensive care unit , <span class="chemical">venlafaxine</span> was discontinued , and no further sequelae were seen . 