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 results are compatible with interference by isoniazid with GABAergic inhibition of cardiac parasympathetic tone .
### Output Text:
These results are compatible with interference by <span class="chemical">isoniazid</span> with GABAergic inhibition of cardiac parasympathetic tone . 