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: A possible drug interaction occurred in a 45 - year - old woman who was taking cisapride for gastroesophageal reflux disorder and diltiazem , an agent that has inhibitory effect on CYP3A4 , for hypertension .
### Output Text:
A possible drug interaction occurred in a 45 - year - old woman who was taking <span class="chemical">cisapride</span> for gastroesophageal reflux disorder and <span class="chemical">diltiazem</span> , an agent that has inhibitory effect on CYP3A4 , for hypertension . 