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 t ( 1 / 2 , z ) of desipramine was longer when desipramine was coadministered with cinacalcet ( 21 . 0 versus 43 . 3 hs ) .
### Output Text:
The t ( 1 / 2 , z ) of <span class="chemical">desipramine</span> was longer when <span class="chemical">desipramine</span> was coadministered with <span class="chemical">cinacalcet</span> ( 21 . 0 versus 43 . 3 hs ) . 