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: Urinary symptoms and quality of life changes in Thai women with overactive bladder after tolterodine treatment .
### Output Text:
Urinary symptoms and quality of life changes in Thai women with overactive bladder after <span class="chemical">tolterodine</span> treatment . 