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: It is unclear whether a coronary CTA strategy would be efficacious in cocaine - associated chest pain , as coronary vasospasm may account for some of the ischemia .
### Output Text:
It is unclear whether a coronary CTA strategy would be efficacious in <span class="chemical">cocaine</span> - associated chest pain , as coronary vasospasm may account for some of the ischemia . 