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: In rare cases , alterations in taste and smell function have been reported for pyrazinamide when combined with other drugs .
### Output Text:
In rare cases , alterations in taste and smell function have been reported for <span class="chemical">pyrazinamide</span> when combined with other drugs . 