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: Dothiepin and amitriptyline were equally effective in alleviating the symptoms of depressive illness , and both were significantly superior to placebo .
### Output Text:
<span class="chemical">Dothiepin</span> and <span class="chemical">amitriptyline</span> were equally effective in alleviating the symptoms of depressive illness , and both were significantly superior to placebo . 