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### Input Text: In 1 patient , marked hypertension was induced by propranolol and the drug had to be withdrawn .
### Output Text:
In 1 patient , marked hypertension was induced by <span class="chemical">propranolol</span> and the drug had to be withdrawn . 