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 these adverse effects occur in some patients , their occurrence could be minimised by knowledge of the molecular effects of sirolimus on the kidney , the use of sirolimus in appropriate patient populations , close monitoring of proteinuria and renal function , use of angiotensin - converting enzyme inhibitors or angiotensin II receptor blockers if proteinuria occurs and withdrawal if needed .
### Output Text:
Although these adverse effects occur in some patients , their occurrence could be minimised by knowledge of the molecular effects of <span class="chemical">sirolimus</span> on the kidney , the use of <span class="chemical">sirolimus</span> in appropriate patient populations , close monitoring of proteinuria and renal function , use of <span class="chemical">angiotensin</span> - converting enzyme inhibitors or <span class="chemical">angiotensin II</span> receptor blockers if proteinuria occurs and withdrawal if needed . 