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: OBJECTIVE : To assess pharmacokinetics , efficacy , and tolerability of oral levetiracetam administered as an adjunct to phenobarbital treatment in cats with poorly controlled suspected idiopathic epilepsy .
### Output Text:
OBJECTIVE : To assess pharmacokinetics , efficacy , and tolerability of oral <span class="chemical">levetiracetam</span> administered as an adjunct to <span class="chemical">phenobarbital</span> treatment in cats with poorly controlled suspected idiopathic epilepsy . 