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: Intraoperative bradycardia and hypotension associated with timolol and pilocarpine eye drops .
### Output Text:
Intraoperative bradycardia and hypotension associated with <span class="chemical">timolol</span> and <span class="chemical">pilocarpine</span> eye drops . 