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: Detailed history obtained retrospectively revealed that the patient took zolmitriptan sparingly only when she had migraines .
### Output Text:
Detailed history obtained retrospectively revealed that the patient took <span class="chemical">zolmitriptan</span> sparingly only when she had migraines . 