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: During the 1 hour after administration of the drug the incidence of ventricular fibrillation or sustained ventricular tachycardia among the 204 patients with acute myocardial infarction was low , 1 . 5 % .
### Output Text:
During the 1 hour after administration of the drug the incidence of ventricular fibrillation or sustained ventricular tachycardia among the 204 patients with acute myocardial infarction was low , 1 . 5 % . 