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 administration of diazepam ( 1 - 30 mg kg - 1 ) produced a dose - dependent decrease in both the mean arterial pressure and the heart rate .
### Output Text:
Intravenous administration of <span class="chemical">diazepam</span> ( 1 - 30 mg kg - 1 ) produced a dose - dependent decrease in both the mean arterial pressure and the heart rate . 