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: We used chloroquine or hydroxychloroquine in 173 of 210 cases and found only one case of chorioretinopathy attributable to these drugs .
### Output Text:
We used <span class="chemical">chloroquine</span> or <span class="chemical">hydroxychloroquine</span> in 173 of 210 cases and found only one case of chorioretinopathy attributable to these drugs . 