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: Moreover , bupivacaine significantly increased COX - 2 gene expression at 48 h as compared with the lidocaine / placebo group .
### Output Text:
Moreover , <span class="chemical">bupivacaine</span> significantly increased COX - 2 gene expression at 48 h as compared with the <span class="chemical">lidocaine</span> / placebo group . 