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 effects of oral administration of caffeine ( 10 mg / kg ) on behavioral ratings , somatic symptoms , blood pressure and plasma levels of 3 - methoxy - 4 - hydroxyphenethyleneglycol ( MHPG ) and cortisol were determined in 17 healthy subjects and 21 patients meeting DSM - III criteria for agoraphobia with panic attacks or panic disorder .
### Output Text:
The effects of oral administration of <span class="chemical">caffeine</span> ( 10 mg / kg ) on behavioral ratings , somatic symptoms , blood pressure and plasma levels of <span class="chemical">3 - methoxy - 4 - hydroxyphenethyleneglycol</span> ( <span class="chemical">MHPG</span> ) and <span class="chemical">cortisol</span> were determined in 17 healthy subjects and 21 patients meeting DSM - III criteria for agoraphobia with panic attacks or panic disorder . 