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: Her medications included desvenlafaxine , and symptoms included nausea , anxiety and confusion .
### Output Text:
Her medications included <span class="chemical">desvenlafaxine</span> , and symptoms included nausea , anxiety and confusion . 