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: SCr increases > or = 0 . 5 mg / dL occurred in 4 . 4 % ( 9 of 204 patients ) after iopamidol and 6 . 7 % ( 14 of 210 patients ) after iodixanol ( P = 0 . 39 ) , whereas rates of SCr increases > or = 25 % were 9 . 8 % and 12 . 4 % , respectively ( P = 0 . 44 ) .
### Output Text:
SCr increases > or = 0 . 5 mg / dL occurred in 4 . 4 % ( 9 of 204 patients ) after <span class="chemical">iopamidol</span> and 6 . 7 % ( 14 of 210 patients ) after <span class="chemical">iodixanol</span> ( P = 0 . 39 ) , whereas rates of SCr increases > or = 25 % were 9 . 8 % and 12 . 4 % , respectively ( P = 0 . 44 ) . 