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 discontinuing cisapride , the QT interval returned to normal and symptoms did not recur .
### Output Text:
After discontinuing <span class="chemical">cisapride</span> , the QT interval returned to normal and symptoms did not recur . 