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: Tiapride , a substituted benzamide derivative closely related to metoclopramide , reduced levodopa - induced peak dose involuntary movements in 16 patients with idiopathic Parkinson ' s disease .
### Output Text:
<span class="chemical">Tiapride</span> , a substituted <span class="chemical">benzamide</span> derivative closely related to <span class="chemical">metoclopramide</span> , reduced <span class="chemical">levodopa</span> - induced peak dose involuntary movements in 16 patients with idiopathic Parkinson ' s disease . 