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: If agitation becomes marked , high - potency neuroleptics ( i . e . , haloperidol ) may be effective .
### Output Text:
If agitation becomes marked , high - potency neuroleptics ( i . e . , <span class="chemical">haloperidol</span> ) may be effective . 