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: Amiodarone was administered to 154 patients who had sustained , symptomatic ventricular tachycardia ( VT ) ( n = 118 ) or a cardiac arrest ( n = 36 ) and who were refractory to conventional antiarrhythmic drugs .
### Output Text:
<span class="chemical">Amiodarone</span> was administered to 154 patients who had sustained , symptomatic ventricular tachycardia ( VT ) ( n = 118 ) or a cardiac arrest ( n = 36 ) and who were refractory to conventional antiarrhythmic drugs . 