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: After 5 minutes , 80 / 115 ( 70 % ) flumazenil - treated patients , compared with 21 / 63 ( 33 % ) placebo - treated patients , were completely awake and alert , as indicated by a score of 5 on the Observer ' s Assessment of Alertness / Sedation Scale .
### Output Text:
After 5 minutes , 80 / 115 ( 70 % ) <span class="chemical">flumazenil</span> - treated patients , compared with 21 / 63 ( 33 % ) placebo - treated patients , were completely awake and alert , as indicated by a score of 5 on the Observer ' s Assessment of Alertness / Sedation Scale . 