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: Encephalopathy during amitriptyline therapy : are neuroleptic malignant syndrome and serotonin syndrome spectrum disorders ?
### Output Text:
Encephalopathy during <span class="chemical">amitriptyline</span> therapy : are neuroleptic malignant syndrome and serotonin syndrome spectrum disorders ? 