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: A prospective clinical trial is suggested to quantify the risk of cardiac complications to patients receiving phenothiazines or tricyclic antidepressant drugs .
### Output Text:
A prospective clinical trial is suggested to quantify the risk of cardiac complications to patients receiving <span class="chemical">phenothiazines</span> or tricyclic antidepressant drugs . 