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: Heart and liver mitochondria were isolated from rats treated for 7 weeks with doxorubicin ( 2 mg / kg sc / week ) , carvedilol ( 1 mg / kg ip / week ) , or the combination of the two drugs .
### Output Text:
Heart and liver mitochondria were isolated from rats treated for 7 weeks with <span class="chemical">doxorubicin</span> ( 2 mg / kg sc / week ) , <span class="chemical">carvedilol</span> ( 1 mg / kg ip / week ) , or the combination of the two drugs . 