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: These data suggest naloxone reverses respiratory paralysis produced by thiopental and involves GABA in its action .
### Output Text:
These data suggest <span class="chemical">naloxone</span> reverses respiratory paralysis produced by <span class="chemical">thiopental</span> and involves <span class="chemical">GABA</span> in its action . 