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: After withdrawal of octreotide in 10 patients without gallstones , 8 patients assessed had return of normal gallbladder contractility within 1 month .
### Output Text:
After withdrawal of <span class="chemical">octreotide</span> in 10 patients without gallstones , 8 patients assessed had return of normal gallbladder contractility within 1 month . 