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: Intravenous propranolol after PPA also decreased blood pressure .
### Output Text:
Intravenous <span class="chemical">propranolol</span> after <span class="chemical">PPA</span> also decreased blood pressure . 