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: This study was undertaken to determine the effect of lidocaine pretreatment on reduction of succinylcholine - induced myalgia in patients undergoing general anesthesia for gynecological surgery .
### Output Text:
This study was undertaken to determine the effect of <span class="chemical">lidocaine</span> pretreatment on reduction of <span class="chemical">succinylcholine</span> - induced myalgia in patients undergoing general anesthesia for gynecological surgery . 