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: Nineteen sexually dysfunctional women receiving either fluoxetine , sertraline , or paroxetine participated in an eight - week , double - blind , placebo - controlled , cross - over study of the effects of ephedrine ( 50 mg ) on self - report measures of sexual desire , arousal , orgasm , and sexual satisfaction .
### Output Text:
Nineteen sexually dysfunctional women receiving either <span class="chemical">fluoxetine</span> , <span class="chemical">sertraline</span> , or <span class="chemical">paroxetine</span> participated in an eight - week , double - blind , placebo - controlled , cross - over study of the effects of <span class="chemical">ephedrine</span> ( 50 mg ) on self - report measures of sexual desire , arousal , orgasm , and sexual satisfaction . 