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: Ethopropazine and benztropine were found to be equally effective in controlling parkinsonian symptoms and were as efficacious as procyclidine , their previous antiparkinsonian drug .
### Output Text:
<span class="chemical">Ethopropazine</span> and <span class="chemical">benztropine</span> were found to be equally effective in controlling parkinsonian symptoms and were as efficacious as <span class="chemical">procyclidine</span> , their previous antiparkinsonian drug . 