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: Safety and compliance with once - daily niacin extended - release / lovastatin as initial therapy in the Impact of Medical Subspecialty on Patient Compliance to Treatment ( IMPACT ) study .
### Output Text:
Safety and compliance with once - daily <span class="chemical">niacin extended - release / lovastatin</span> as initial therapy in the Impact of Medical Subspecialty on Patient Compliance to Treatment ( IMPACT ) study . 