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: We report the case of a previously healthy 19 - year - old man with no known drug allergies in whom angioedema with significant tongue swelling and protrusion developed within 10 minutes of the administration of a single IV dose of droperidol .
### Output Text:
We report the case of a previously healthy 19 - year - old man with no known drug allergies in whom angioedema with significant tongue swelling and protrusion developed within 10 minutes of the administration of a single IV dose of <span class="chemical">droperidol</span> . 