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: The results indicate that fluvoxamine given repeatedly acts differently than citalopram , another selective serotonin uptake inhibitor , and differs also from other antidepressant drugs .
### Output Text:
The results indicate that <span class="chemical">fluvoxamine</span> given repeatedly acts differently than <span class="chemical">citalopram</span> , another selective <span class="chemical">serotonin</span> uptake inhibitor , and differs also from other antidepressant drugs . 