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: Thus , clinicians should address patients ' concerns about adverse effects and attempt to choose medications that will improve their patients ' quality of life as well as overall health .
### Output Text:
Thus , clinicians should address patients ' concerns about adverse effects and attempt to choose medications that will improve their patients ' quality of life as well as overall health . 