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: As no other medications known to effect serum potassium had been given concomitantly , this course of events is suggestive of a cause - and - effect relationship between sulindac and hyperkalemia .
### Output Text:
As no other medications known to effect serum <span class="chemical">potassium</span> had been given concomitantly , this course of events is suggestive of a cause - and - effect relationship between <span class="chemical">sulindac</span> and hyperkalemia . 