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: The authors report here a depressed patient comorbid with postprandial dyspepsia who developed RLS after mirtazapine had been added to his domperidone therapy .
### Output Text:
The authors report here a depressed patient comorbid with postprandial dyspepsia who developed RLS after <span class="chemical">mirtazapine</span> had been added to his <span class="chemical">domperidone</span> therapy . 