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: It is suggested that sevoflurane reduces the convulsive effect of lidocaine toxicity but carries some risk due to circulatory depression .
### Output Text:
It is suggested that <span class="chemical">sevoflurane</span> reduces the convulsive effect of <span class="chemical">lidocaine</span> toxicity but carries some risk due to circulatory depression . 