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: When serum prolactin levels normalized in all four subjects ( mean 11 . 2 + / - 10 . 9 ng / mL ) , the cabergoline dose was reduced to 1 mg / week in three of four subjects .
### Output Text:
When serum prolactin levels normalized in all four subjects ( mean 11 . 2 + / - 10 . 9 ng / mL ) , the <span class="chemical">cabergoline</span> dose was reduced to 1 mg / week in three of four subjects . 