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: During the follow - up of our patient , penicillamine was interrupted after the appearance of a lichenoid dermatitis , and zinc acetate permitted to continue the successful treatment of the patient without side - effects .
### Output Text:
During the follow - up of our patient , <span class="chemical">penicillamine</span> was interrupted after the appearance of a lichenoid dermatitis , and <span class="chemical">zinc acetate</span> permitted to continue the successful treatment of the patient without side - effects . 