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: Levodopa is the most effective symptomatic therapy for Parkinson ' s disease , but its chronic use could lead to chronic adverse outcomes , such as motor fluctuations , dyskinesia and visual hallucinations .
### Output Text:
<span class="chemical">Levodopa</span> is the most effective symptomatic therapy for Parkinson ' s disease , but its chronic use could lead to chronic adverse outcomes , such as motor fluctuations , dyskinesia and visual hallucinations . 