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: BACKGROUND : A previous randomized controlled trial evaluating the use of spironolactone in heart failure patients reported a low risk of hyperkalemia ( 2 % ) and renal insufficiency ( 0 % ) .
### Output Text:
BACKGROUND : A previous randomized controlled trial evaluating the use of <span class="chemical">spironolactone</span> in heart failure patients reported a low risk of hyperkalemia ( 2 % ) and renal insufficiency ( 0 % ) . 