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: After the addition of a minimal dose of clonidine ( 0 . 15 mg bid ) , she developed complete AV block and severe hypotension , which resolved upon cessation of all medications .
### Output Text:
After the addition of a minimal dose of <span class="chemical">clonidine</span> ( 0 . 15 mg bid ) , she developed complete AV block and severe hypotension , which resolved upon cessation of all medications . 