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: The seizures were successfully treated with sodium thiopental in addition to succinylcholine in 1 patient .
### Output Text:
The seizures were successfully treated with <span class="chemical">sodium thiopental</span> in addition to <span class="chemical">succinylcholine</span> in 1 patient . 