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: Acute confusion induced by acetazolamide is a well known adverse drug reaction in patients with renal impairment .
### Output Text:
Acute confusion induced by <span class="chemical">acetazolamide</span> is a well known adverse drug reaction in patients with renal impairment . 