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: We have examined the effect of systemic administration of ketamine and lidocaine on brush - evoked ( dynamic ) pain and punctate - evoked ( static ) hyperalgesia induced by capsaicin .
### Output Text:
We have examined the effect of systemic administration of <span class="chemical">ketamine</span> and <span class="chemical">lidocaine</span> on brush - evoked ( dynamic ) pain and punctate - evoked ( static ) hyperalgesia induced by <span class="chemical">capsaicin</span> . 