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: Careful attention to renal function and potassium balance in patients receiving indomethacin or other nonsteroidal anti - inflammatory agents , particularly in those patients with diabetes mellitus or preexisting renal disease , will help prevent this potentially serious complication .
### Output Text:
Careful attention to renal function and <span class="chemical">potassium</span> balance in patients receiving <span class="chemical">indomethacin</span> or other nonsteroidal anti - inflammatory agents , particularly in those patients with diabetes mellitus or preexisting renal disease , will help prevent this potentially serious complication . 