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: Administration of parenteral quinine must be done carefully and with good observation because of its pro - arrhythmic effect , especially in older patients who have heart diseases or patients with electrolyte disorder ( hypokalemia ) which frequently occurs due to vomiting and or diarrhea in malaria cases .
### Output Text:
Administration of parenteral <span class="chemical">quinine</span> must be done carefully and with good observation because of its pro - arrhythmic effect , especially in older patients who have heart diseases or patients with electrolyte disorder ( hypokalemia ) which frequently occurs due to vomiting and or diarrhea in malaria cases . 