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: If the patient has not aborted by then the oxytocin should be discontinued for 10 to 12 hours in order to perform electrolyte determinations and correct any electrolyte imbalance .
### Output Text:
If the patient has not aborted by then the <span class="chemical">oxytocin</span> should be discontinued for 10 to 12 hours in order to perform electrolyte determinations and correct any electrolyte imbalance . 