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: OBJECTIVE : To determine the safety and efficacy of adjunctive bupropion sustained - release ( SR ) on male sexual dysfunction ( SD ) induced by a selective serotonin reuptake inhibitor ( SSRI ) , as SD is a common side - effect of SSRIs and the most effective treatments have yet to be determined .
### Output Text:
OBJECTIVE : To determine the safety and efficacy of adjunctive <span class="chemical">bupropion</span> sustained - release ( SR ) on male sexual dysfunction ( SD ) induced by a <span class="chemical">selective serotonin reuptake inhibitor</span> ( <span class="chemical">SSRI</span> ) , as SD is a common side - effect of <span class="chemical">SSRIs</span> and the most effective treatments have yet to be determined . 