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: A repeated treatment with fluvoxamine ( twice daily for 14 days ) potentiated in mice and in rats ( weaker ) the amphetamine - induced hyperactivity .
### Output Text:
A repeated treatment with <span class="chemical">fluvoxamine</span> ( twice daily for 14 days ) potentiated in mice and in rats ( weaker ) the <span class="chemical">amphetamine</span> - induced hyperactivity . 