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: Significant blockade of cocaine toxicity was observed with the higher dose of GNC92H2 ( 190 mg / kg ) , where premorbid behaviors were reduced up to 40 % , seizures up to 77 % and death by 72 % .
### Output Text:
Significant blockade of <span class="chemical">cocaine</span> toxicity was observed with the higher dose of <span class="chemical">GNC92H2</span> ( 190 mg / kg ) , where premorbid behaviors were reduced up to 40 % , seizures up to 77 % and death by 72 % . 