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 conclude that pentoxyifylline does not inhibit dipyridamole - induced coronary hyperemia even at high doses .
### Output Text:
We conclude that <span class="chemical">pentoxyifylline</span> does not inhibit <span class="chemical">dipyridamole</span> - induced coronary hyperemia even at high doses . 