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: Both patients recovered quickly after stopping glyburide therapy and have remained well for a follow - up period of 1 year .
### Output Text:
Both patients recovered quickly after stopping <span class="chemical">glyburide</span> therapy and have remained well for a follow - up period of 1 year . 