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: Oral administration of CBZ as an aqueous suspension every 8 h at a dose of 250 mg / kg was continuously protective against HFDE - induced seizures and was minimally toxic as measured by weight gain over 8 weeks of treatment .
### Output Text:
Oral administration of <span class="chemical">CBZ</span> as an aqueous suspension every 8 h at a dose of 250 mg / kg was continuously protective against <span class="chemical">HFDE</span> - induced seizures and was minimally toxic as measured by weight gain over 8 weeks of treatment . 