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: A CD50 dose of local anesthetic ( causing convulsions in 50 % of mice ) was fatal in 90 % of bupivacaine - induced seizures , in 57 % of the chloroprocaine group , and in 6 % of the lidocaine group .
### Output Text:
A CD50 dose of local anesthetic ( causing convulsions in 50 % of mice ) was fatal in 90 % of <span class="chemical">bupivacaine</span> - induced seizures , in 57 % of the <span class="chemical">chloroprocaine</span> group , and in 6 % of the <span class="chemical">lidocaine</span> group . 