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: Both the pressor and bradycardia effects of cirazoline were abolished in chronic prazosin treated SHR ( n = 4 ) as compared to the untreated SHR ( n = 4 ) .
### Output Text:
Both the pressor and bradycardia effects of <span class="chemical">cirazoline</span> were abolished in chronic <span class="chemical">prazosin</span> treated SHR ( n = 4 ) as compared to the untreated SHR ( n = 4 ) . 