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: Acute liver failure with concurrent bupropion and carbimazole therapy .
### Output Text:
Acute liver failure with concurrent <span class="chemical">bupropion</span> and <span class="chemical">carbimazole</span> therapy . 