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: Patients who are switched from cyclosporine to tacrolimus or vice versa should be closely monitored for the signs and symptoms of recurrent TMA .
### Output Text:
Patients who are switched from <span class="chemical">cyclosporine</span> to <span class="chemical">tacrolimus</span> or vice versa should be closely monitored for the signs and symptoms of recurrent TMA . 