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: Stroke followed cocaine use by inhalation , intranasal , intravenous , and intramuscular routes .
### Output Text:
Stroke followed <span class="chemical">cocaine</span> use by inhalation , intranasal , intravenous , and intramuscular routes . 