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: Recently , synthetic fibrinolysis inhibitors such as tranexamic acid ( tAMCA ) have been considered as substitutes for aprotinin .
### Output Text:
Recently , synthetic fibrinolysis inhibitors such as <span class="chemical">tranexamic acid</span> ( <span class="chemical">tAMCA</span> ) have been considered as substitutes for aprotinin . 