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: Symptom scores relating to the severity of constipation were lower in cisapride - treated constipation - predominant IBS patients [ score , 54 + / - 5 versus 67 + / - 14 mm , cisapride versus placebo ( P < 0 . 05 ) ; pretreatment , 62 + / - 19 mm ] .
### Output Text:
Symptom scores relating to the severity of constipation were lower in <span class="chemical">cisapride</span> - treated constipation - predominant IBS patients [ score , 54 + / - 5 versus 67 + / - 14 mm , <span class="chemical">cisapride</span> versus placebo ( P < 0 . 05 ) ; pretreatment , 62 + / - 19 mm ] . 