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: Inappropriate use of carbamazepine and vigabatrin in typical absence seizures .
### Output Text:
Inappropriate use of <span class="chemical">carbamazepine</span> and <span class="chemical">vigabatrin</span> in typical absence seizures . 