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: Medical treatment was initiated at a daily dose of 20 mg paroxetine and 1 . 2 mg alprazolam .
### Output Text:
Medical treatment was initiated at a daily dose of 20 mg <span class="chemical">paroxetine</span> and 1 . 2 mg <span class="chemical">alprazolam</span> . 