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: However , the administration of lamivudine , a reverse transcriptase inhibitor , for 23 months dramatically improved her liver severity .
### Output Text:
However , the administration of <span class="chemical">lamivudine</span> , a reverse transcriptase inhibitor , for 23 months dramatically improved her liver severity . 