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 may be relevant to the use of FZP in clinical situations in which there is increased neural excitability , such as epilepsy or sedative - hypnotic drug withdrawal .
### Output Text:
These results may be relevant to the use of <span class="chemical">FZP</span> in clinical situations in which there is increased neural excitability , such as epilepsy or sedative - hypnotic drug withdrawal . 