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: This study measured the objective and subjective neurocognitive effects of a single 10 - mg dose of immediate - release oxycodone in healthy , older ( > 65 years ) , and middle - aged ( 35 to 55 years ) adults who were not suffering from chronic or significant daily pain .
### Output Text:
This study measured the objective and subjective neurocognitive effects of a single 10 - mg dose of immediate - release <span class="chemical">oxycodone</span> in healthy , older ( > 65 years ) , and middle - aged ( 35 to 55 years ) adults who were not suffering from chronic or significant daily pain . 