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: DISCUSSION : The risk of rhabdomyolysis is increased in the presence of concomitant drugs that inhibit simvastatin metabolism .
### Output Text:
DISCUSSION : The risk of rhabdomyolysis is increased in the presence of concomitant drugs that inhibit <span class="chemical">simvastatin</span> metabolism . 