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: Akathisia appeared to be a common side effect of fluoxetine and generally responded well to treatment with the beta - adrenergic antagonist propranolol , dose reduction , or both .
### Output Text:
Akathisia appeared to be a common side effect of <span class="chemical">fluoxetine</span> and generally responded well to treatment with the beta - adrenergic antagonist <span class="chemical">propranolol</span> , dose reduction , or both . 