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 AND CLINICAL RELEVANCE : Results suggested that levetiracetam is well tolerated in cats and may be useful as an adjunct to phenobarbital treatment in cats with idiopathic epilepsy .
### Output Text:
CONCLUSIONS AND CLINICAL RELEVANCE : Results suggested that <span class="chemical">levetiracetam</span> is well tolerated in cats and may be useful as an adjunct to <span class="chemical">phenobarbital</span> treatment in cats with idiopathic epilepsy . 