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: Atracurium besylate , a short - acting benzylisoquinolinium NMBA that is eliminated independently of renal or hepatic function , has also been associated with persistent paralysis , but only when used with corticosteroids .
### Output Text:
<span class="chemical">Atracurium besylate</span> , a short - acting <span class="chemical">benzylisoquinolinium</span> NMBA that is eliminated independently of renal or hepatic function , has also been associated with persistent paralysis , but only when used with corticosteroids . 