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: In cisapride - treated diarrhoea - predominant patients the mean contraction amplitude was higher ( 29 . 3 + / - 3 . 2 versus 24 . 9 + / - 2 . 6 mm Hg , cisapride versus placebo ( P < 0 . 001 ) ; pretreatment , 25 . 7 + / - 6 . 0 mm Hg ) , the mean contraction duration longer ( 3 . 4 + / - 0 . 2 versus 3 . 0 + / - 0 . 2 sec , cisapride versus placebo ( P < 0 . 001 ) ; pretreatment , 3 . 1 + / - 0 . 5 sec ) , and the mean contraction frequency lower ( 2 . 0 + / - 0 . 2 versus 2 . 5 + / - 0 . 4 cont . / min , cisapride versus placebo ( P < 0 . 001 ) ; pretreatment , 2 . 5 + / - 1 . 1 cont . / min ] than patients treated with placebo .
### Output Text:
In <span class="chemical">cisapride</span> - treated diarrhoea - predominant patients the mean contraction amplitude was higher ( 29 . 3 + / - 3 . 2 versus 24 . 9 + / - 2 . 6 mm Hg , <span class="chemical">cisapride</span> versus placebo ( P < 0 . 001 ) ; pretreatment , 25 . 7 + / - 6 . 0 mm Hg ) , the mean contraction duration longer ( 3 . 4 + / - 0 . 2 versus 3 . 0 + / - 0 . 2 sec , <span class="chemical">cisapride</span> versus placebo ( P < 0 . 001 ) ; pretreatment , 3 . 1 + / - 0 . 5 sec ) , and the mean contraction frequency lower ( 2 . 0 + / - 0 . 2 versus 2 . 5 + / - 0 . 4 cont . / min , <span class="chemical">cisapride</span> versus placebo ( P < 0 . 001 ) ; pretreatment , 2 . 5 + / - 1 . 1 cont . / min ] than patients treated with placebo . 