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: Recurrent seizures were treated with diazepam and broad complex tachycardia was successfully treated with adenosine .
### Output Text:
Recurrent seizures were treated with <span class="chemical">diazepam</span> and broad complex tachycardia was successfully treated with <span class="chemical">adenosine</span> . 