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: Rizatriptan was also superior to ergotamine / caffeine in the proportions of patients with no nausea , vomiting , phonophobia or photophobia and for patients with normal function 2 h after drug intake ( p < or = 0 . 001 ) .
### Output Text:
<span class="chemical">Rizatriptan</span> was also superior to <span class="chemical">ergotamine</span> / <span class="chemical">caffeine</span> in the proportions of patients with no nausea , vomiting , phonophobia or photophobia and for patients with normal function 2 h after drug intake ( p < or = 0 . 001 ) . 