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: Trial medication was 2 . 5 mg enalapril or 0 . 5 prazosin .
### Output Text:
Trial medication was 2 . 5 mg <span class="chemical">enalapril</span> or 0 . 5 <span class="chemical">prazosin</span> . 