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: BACKGROUND : The optimal dosing regimens of lipid emulsion , epinephrine , or both are not yet determined in neonates in cases of local anaesthetic systemic toxicity ( LAST ) .
### Output Text:
BACKGROUND : The optimal dosing regimens of lipid emulsion , <span class="chemical">epinephrine</span> , or both are not yet determined in neonates in cases of local anaesthetic systemic toxicity ( LAST ) . 