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: This study was designed to assess the ability of spironolactone to reduce potassium requirements and to prevent hypokalemia in neutropenic patients on AmB treatment .
### Output Text:
This study was designed to assess the ability of <span class="chemical">spironolactone</span> to reduce <span class="chemical">potassium</span> requirements and to prevent hypokalemia in neutropenic patients on <span class="chemical">AmB</span> treatment . 