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: Mefenamic acid - induced neutropenia and renal failure in elderly females with hypothyroidism .
### Output Text:
<span class="chemical">Mefenamic acid</span> - induced neutropenia and renal failure in elderly females with hypothyroidism . 