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: Five patients receiving fluoxetine for the treatment of obsessive compulsive disorder or major depression developed akathisia .
### Output Text:
Five patients receiving <span class="chemical">fluoxetine</span> for the treatment of obsessive compulsive disorder or major depression developed akathisia . 