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: Capsaicin 100 micrograms was injected intradermally on the volar forearm followed by an i . v . infusion of ketamine ( bolus 0 . 1 mg kg - 1 over 10 min followed by infusion of 7 micrograms kg - 1 min - 1 ) , lidocaine 5 mg kg - 1 or saline for 50 min .
### Output Text:
<span class="chemical">Capsaicin</span> 100 micrograms was injected intradermally on the volar forearm followed by an i . v . infusion of <span class="chemical">ketamine</span> ( bolus 0 . 1 mg kg - 1 over 10 min followed by infusion of 7 micrograms kg - 1 min - 1 ) , <span class="chemical">lidocaine</span> 5 mg kg - 1 or saline for 50 min . 