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: Antagonism of diazepam - induced sedative effects by Ro15 - 1788 in patients after surgery under lumbar epidural block .
### Output Text:
Antagonism of <span class="chemical">diazepam</span> - induced sedative effects by <span class="chemical">Ro15 - 1788</span> in patients after surgery under lumbar epidural block . 