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: The patient was diagnosed with drug - induced baboon syndrome based on his history , which included prior sensitivity to topical ketoconazole , a physical examination , and histopathological findings .
### Output Text:
The patient was diagnosed with drug - induced baboon syndrome based on his history , which included prior sensitivity to topical <span class="chemical">ketoconazole</span> , a physical examination , and histopathological findings . 