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: Metoprolol was dosed to achieve a resting predobutamine heart rate below 65 beats / minute or a total intravenous dose of 20 mg .
### Output Text:
<span class="chemical">Metoprolol</span> was dosed to achieve a resting <span class="chemical">predobutamine</span> heart rate below 65 beats / minute or a total intravenous dose of 20 mg . 