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: The narrow therapeutic window observed with haloperidol may also apply to other neuroleptics used in Alzheimer ' s disease patients with psychosis and disruptive behaviors .
### Output Text:
The narrow therapeutic window observed with <span class="chemical">haloperidol</span> may also apply to other neuroleptics used in Alzheimer ' s disease patients with psychosis and disruptive behaviors . 