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: RESULTS : Sixty - seven of 926 patients ( 7 . 2 % ) required discontinuation of spironolactone due to hyperkalemia ( n = 33 ) or renal failure ( n = 34 ) .
### Output Text:
RESULTS : Sixty - seven of 926 patients ( 7 . 2 % ) required discontinuation of <span class="chemical">spironolactone</span> due to hyperkalemia ( n = 33 ) or renal failure ( n = 34 ) . 