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: Further study is needed to determine the optimal dosage and to identify risk factors that increase individual vulnerability to fluoxetine induced mania in adolescents .
### Output Text:
Further study is needed to determine the optimal dosage and to identify risk factors that increase individual vulnerability to <span class="chemical">fluoxetine</span> induced mania in adolescents . 