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: All patients had bilateral symptoms and their levodopa equivalent dosing were analysed .
### Output Text:
All patients had bilateral symptoms and their <span class="chemical">levodopa</span> equivalent dosing were analysed . 