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: The case shows that prolonged jaw rigidity and myalgia may occur after suxamethonium in patients with atypical cholinesterase despite pretreatment with pancuronium .
### Output Text:
The case shows that prolonged jaw rigidity and myalgia may occur after <span class="chemical">suxamethonium</span> in patients with atypical cholinesterase despite pretreatment with <span class="chemical">pancuronium</span> . 