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: Although with current ulcer therapy ( H - 2 blockers , omeprazole , and sucralfate ) , the frequency of milk - alkali syndrome has decreased significantly , the classic triad of hypercalcemia , alkalosis , and renal impairment remains the hallmark of the syndrome .
### Output Text:
Although with current ulcer therapy ( H - 2 blockers , <span class="chemical">omeprazole</span> , and <span class="chemical">sucralfate</span> ) , the frequency of milk - alkali syndrome has decreased significantly , the classic triad of hypercalcemia , alkalosis , and renal impairment remains the hallmark of the syndrome . 