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: Because carbamazepine is widely used in the treatment of many neurologic and psychiatric conditions , the recognition of the latter syndrome has important implications for the use of this drug in elderly patients .
### Output Text:
Because <span class="chemical">carbamazepine</span> is widely used in the treatment of many neurologic and psychiatric conditions , the recognition of the latter syndrome has important implications for the use of this drug in elderly patients . 