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: Its prolonged use or overuse has been associated with seizures , intracerebral hemorrhage , neuropsychiatric symptoms , and nonhemorrhagic cerebral infarction .
### Output Text:
Its prolonged use or overuse has been associated with seizures , intracerebral hemorrhage , neuropsychiatric symptoms , and nonhemorrhagic cerebral infarction . 