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 : Subjects ( n = 139 ) were 72 women and 67 men , aged 40 . 8 + / - 12 . 1 years , hospitalized for 24 . 9 + / - 23 . 3 days , and given clozapine , gradually increased to an average daily dose of 282 + / - 203 mg ( 3 . 45 + / - 2 . 45 mg / kg ) for 18 . 9 + / - 16 . 4 days .
### Output Text:
RESULTS : Subjects ( n = 139 ) were 72 women and 67 men , aged 40 . 8 + / - 12 . 1 years , hospitalized for 24 . 9 + / - 23 . 3 days , and given <span class="chemical">clozapine</span> , gradually increased to an average daily dose of 282 + / - 203 mg ( 3 . 45 + / - 2 . 45 mg / kg ) for 18 . 9 + / - 16 . 4 days . 