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: Pulmonary hypertension developed after administration of a somatostatin analogue , octreotide , to enhance resolution of the fistula .
### Output Text:
Pulmonary hypertension developed after administration of a somatostatin analogue , <span class="chemical">octreotide</span> , to enhance resolution of the fistula . 