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: During the course of haloperidol infusions , significant hyperprolactinemia was found , together with an abolished pituitary response to LH - RH , as compared with responses of control subjects .
### Output Text:
During the course of <span class="chemical">haloperidol</span> infusions , significant hyperprolactinemia was found , together with an abolished pituitary response to LH - RH , as compared with responses of control subjects . 