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: The introduction of drugs that could induce hypotension with different pharmacological actions would be advantageous because side effects unique to a specific drug could be minimized by selecting appropriate therapy .
### Output Text:
The introduction of drugs that could induce hypotension with different pharmacological actions would be advantageous because side effects unique to a specific drug could be minimized by selecting appropriate therapy . 