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: Diarrhoea - predominant IBS patients had a higher pain score after cisapride therapy [ score , 55 + / - 15 versus 34 + / - 12 mm , cisapride versus placebo ( P < 0 . 05 ) ; pretreatment , 67 + / - 19 mm ] .
### Output Text:
Diarrhoea - predominant IBS patients had a higher pain score after <span class="chemical">cisapride</span> therapy [ score , 55 + / - 15 versus 34 + / - 12 mm , <span class="chemical">cisapride</span> versus placebo ( P < 0 . 05 ) ; pretreatment , 67 + / - 19 mm ] . 