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 initial dose of labetalol for lowering blood pressure was similar , 0 . 52 - 0 . 59 mg / kg , in all the groups .
### Output Text:
The initial dose of <span class="chemical">labetalol</span> for lowering blood pressure was similar , 0 . 52 - 0 . 59 mg / kg , in all the groups . 