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: Six of the patients received more than 15 mg paclitaxel and suffered from moderate to severe brain edema , while the remaining patients received only a total of 15 mg paclitaxel .
### Output Text:
Six of the patients received more than 15 mg <span class="chemical">paclitaxel</span> and suffered from moderate to severe brain edema , while the remaining patients received only a total of 15 mg <span class="chemical">paclitaxel</span> . 