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: Men who received bupropion had a significant increase in the total IIEF score ( 54 . 4 % vs 1 . 2 % ; P = 0 . 003 ) , and in the five different domains of the IIEF .
### Output Text:
Men who received <span class="chemical">bupropion</span> had a significant increase in the total IIEF score ( 54 . 4 % vs 1 . 2 % ; P = 0 . 003 ) , and in the five different domains of the IIEF . 