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: This patient presented with symptoms of neuroleptic malignant syndrome ( NMS ) , thus demonstrating that NMS - like symptoms can occur after combined paroxetine and alprazolam treatment .
### Output Text:
This patient presented with symptoms of neuroleptic malignant syndrome ( NMS ) , thus demonstrating that NMS - like symptoms can occur after combined <span class="chemical">paroxetine</span> and <span class="chemical">alprazolam</span> treatment . 