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: Patients also received dietary counseling , educational materials , and reminders to call a toll - free number that provided further education about dyslipidemia and niacin extended - release / lovastatin .
### Output Text:
Patients also received dietary counseling , educational materials , and reminders to call a toll - free number that provided further education about dyslipidemia and <span class="chemical">niacin extended - release / lovastatin</span> . 