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: The patients concurrent medications included didanosine , hydroxyzine , promethazine , hydrocortisone , and prochlorperazine .
### Output Text:
The patients concurrent medications included <span class="chemical">didanosine</span> , <span class="chemical">hydroxyzine</span> , <span class="chemical">promethazine</span> , <span class="chemical">hydrocortisone</span> , and <span class="chemical">prochlorperazine</span> . 