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: Thirteen patients have been treated to date with 1 . 5 % or 2 % topical glycopyrrolate .
### Output Text:
Thirteen patients have been treated to date with 1 . 5 % or 2 % topical <span class="chemical">glycopyrrolate</span> . 