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 : The maximum antihyperalgesic effect achievable with nonsedating doses of morphine may be increased significantly when the drug is used in combination with CNSB002 .
### Output Text:
CONCLUSIONS : The maximum antihyperalgesic effect achievable with nonsedating doses of <span class="chemical">morphine</span> may be increased significantly when the drug is used in combination with <span class="chemical">CNSB002</span> . 