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: In this report we describe an unusual case of reversible levodopa - induced Oromandibular dystonia ( OMD ) in a PSP patient to highlight the importance of recognizing this drug related complication in the management of PSP , and discuss the possible underlying pathophysiology .
### Output Text:
In this report we describe an unusual case of reversible <span class="chemical">levodopa</span> - induced Oromandibular dystonia ( OMD ) in a PSP patient to highlight the importance of recognizing this drug related complication in the management of PSP , and discuss the possible underlying pathophysiology . 