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 investigated the effects of clentiazem , a 1 , 5 - benzothiazepine calcium antagonist , on epinephrine - induced cardiomyopathy in rats .
### Output Text:
We investigated the effects of <span class="chemical">clentiazem</span> , a <span class="chemical">1 , 5 - benzothiazepine</span> <span class="chemical">calcium</span> antagonist , on <span class="chemical">epinephrine</span> - induced cardiomyopathy in rats . 