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: Because treatments for heart failure have changed since the benefits of spironolactone were reported , the prevalence of these complications may differ in current clinical practice .
### Output Text:
Because treatments for heart failure have changed since the benefits of <span class="chemical">spironolactone</span> were reported , the prevalence of these complications may differ in current clinical practice . 