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: It appears that the protection from extrapyramidal side effects observed with risperidone does not ensure protection from neuroleptic malignant syndrome .
### Output Text:
It appears that the protection from extrapyramidal side effects observed with <span class="chemical">risperidone</span> does not ensure protection from neuroleptic malignant syndrome . 