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: RESULTS : Of 405 patients not previously receiving an ACE inhibitor , doses in only 4 . 2 % could not be titrated to the medium doses required for randomization because of symptoms possibly related to hypotension ( 2 . 0 % ) or because of renal dysfunction or hyperkalemia ( 2 . 3 % ) .
### Output Text:
RESULTS : Of 405 patients not previously receiving an <span class="chemical">ACE inhibitor</span> , doses in only 4 . 2 % could not be titrated to the medium doses required for randomization because of symptoms possibly related to hypotension ( 2 . 0 % ) or because of renal dysfunction or hyperkalemia ( 2 . 3 % ) . 