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: Since she had no blood pressure elevation at initial diagnosis and none following discontinuation of the Imipramine ( when she was in florid relapse ) , we believe that this drug rather than her underlying disease alone caused her hypertension .
### Output Text:
Since she had no blood pressure elevation at initial diagnosis and none following discontinuation of the <span class="chemical">Imipramine</span> ( when she was in florid relapse ) , we believe that this drug rather than her underlying disease alone caused her hypertension . 