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 administration of intermittent intravenous infusions of cimetidine is infrequently associated with the development of bradyarrhythmias .
### Output Text:
The administration of intermittent intravenous infusions of <span class="chemical">cimetidine</span> is infrequently associated with the development of bradyarrhythmias . 