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: CONCLUSIONS : Pharmacokinetic differences in statins are an important consideration for assessing the risk of potential drug interactions .
### Output Text:
CONCLUSIONS : Pharmacokinetic differences in <span class="chemical">statins</span> are an important consideration for assessing the risk of potential drug interactions . 