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 studied the effects of 1 week of oral hydrocortisone ( 200 mg / day ) on blood pressure , cardiac output , total peripheral resistance , forearm vascular resistance , and norepinephrine spillover to plasma in eight healthy male volunteers .
### Output Text:
We studied the effects of 1 week of oral <span class="chemical">hydrocortisone</span> ( 200 mg / day ) on blood pressure , cardiac output , total peripheral resistance , forearm vascular resistance , and <span class="chemical">norepinephrine</span> spillover to plasma in eight healthy male volunteers . 