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: Accordingly , the present , prospective double - blind study compares prilocaine with lidocaine and bupivacaine with respect to duration of action and relative risk of TNSs .
### Output Text:
Accordingly , the present , prospective double - blind study compares <span class="chemical">prilocaine</span> with <span class="chemical">lidocaine</span> and <span class="chemical">bupivacaine</span> with respect to duration of action and relative risk of TNSs . 