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 reduction in the levodopa dose is useful in controlling drug - induced dyskinesias .
### Output Text:
The reduction in the <span class="chemical">levodopa</span> dose is useful in controlling drug - induced dyskinesias . 