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: We report the case of a 63 - year - old female who was treated with methylphenidate due to hyperactivity and suffered from multiple ischaemic strokes .
### Output Text:
We report the case of a 63 - year - old female who was treated with <span class="chemical">methylphenidate</span> due to hyperactivity and suffered from multiple ischaemic strokes . 