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: We evaluated the severity of motor disability and dyskinesias in seven levodopa - responsive patients with Parkinson ' s disease after an acute challenge with the mixed dopamine agonist , apomorphine , before and after the administration of fluoxetine ( 20 mg twice per day ) for 11 + / - 1 days .
### Output Text:
We evaluated the severity of motor disability and dyskinesias in seven <span class="chemical">levodopa</span> - responsive patients with Parkinson ' s disease after an acute challenge with the mixed <span class="chemical">dopamine</span> agonist , <span class="chemical">apomorphine</span> , before and after the administration of <span class="chemical">fluoxetine</span> ( 20 mg twice per day ) for 11 + / - 1 days . 