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: Two of 14 patients with Cushing ' s syndrome treated on a long - term basis with ketoconazole developed sustained hypertension .
### Output Text:
Two of 14 patients with Cushing ' s syndrome treated on a long - term basis with <span class="chemical">ketoconazole</span> developed sustained hypertension . 