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: When given intraperitoneally , bupivacaine thus was only about twice as toxic as lidocaine and four times as toxic as chloroprocaine .
### Output Text:
When given intraperitoneally , <span class="chemical">bupivacaine</span> thus was only about twice as toxic as <span class="chemical">lidocaine</span> and four times as toxic as <span class="chemical">chloroprocaine</span> . 