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: After he achieved complete remission , he received high - dose cytosine arabinoside treatment ( 2 g / m2 twice a day for 5 days ; total , 20 g / m2 ) as consolidation therapy .
### Output Text:
After he achieved complete remission , he received high - dose <span class="chemical">cytosine arabinoside</span> treatment ( 2 g / m2 twice a day for 5 days ; total , 20 g / m2 ) as consolidation therapy . 