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: Epidemiological data suggest that fluoxetine exposure prenatally increases the prevalence of persistent pulmonary hypertension syndrome of the newborn .
### Output Text:
Epidemiological data suggest that <span class="chemical">fluoxetine</span> exposure prenatally increases the prevalence of persistent pulmonary hypertension syndrome of the newborn . 