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: It is concluded that this protection by carvedilol against both the structural and functional cardiac tissue damage may afford significant clinical advantage in minimizing the dose - limiting mitochondrial dysfunction and cardiomyopathy that accompanies long - term doxorubicin therapy in cancer patients .
### Output Text:
It is concluded that this protection by <span class="chemical">carvedilol</span> against both the structural and functional cardiac tissue damage may afford significant clinical advantage in minimizing the dose - limiting mitochondrial dysfunction and cardiomyopathy that accompanies long - term <span class="chemical">doxorubicin</span> therapy in cancer patients . 