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: Although urinary incontinence is listed as one side effect of these drugs in their package inserts there is only one report in the literature .
### Output Text:
Although urinary incontinence is listed as one side effect of these drugs in their package inserts there is only one report in the literature . 