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: Tetrabenazine should be administered very carefully in combination with other neuroleptic drugs , particularly in patients with a worsening general condition .
### Output Text:
<span class="chemical">Tetrabenazine</span> should be administered very carefully in combination with other <span class="chemical">neuroleptic drugs</span> , particularly in patients with a worsening general condition . 