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: Pharmacokinetic / pharmacodynamic assessment of the effects of E4031 , cisapride , terfenadine and terodiline on monophasic action potential duration in dog .
### Output Text:
Pharmacokinetic / pharmacodynamic assessment of the effects of <span class="chemical">E4031</span> , <span class="chemical">cisapride</span> , <span class="chemical">terfenadine</span> and <span class="chemical">terodiline</span> on monophasic action potential duration in dog . 