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 actions of both drugs were increased by anticholinergic agents , and there was a close correlation between the daily maintenance dose of each drug needed to control acid secretion .
### Output Text:
The actions of both drugs were increased by anticholinergic agents , and there was a close correlation between the daily maintenance dose of each drug needed to control acid secretion . 