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 current study identified the optimal dose of rocuronium to prevent succinylcholine - induced fasciculation and myalgia and evaluated the influence of rocuronium on the speed of onset produced by succinylcholine .
### Output Text:
The current study identified the optimal dose of <span class="chemical">rocuronium</span> to prevent <span class="chemical">succinylcholine</span> - induced fasciculation and myalgia and evaluated the influence of <span class="chemical">rocuronium</span> on the speed of onset produced by <span class="chemical">succinylcholine</span> . 