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: MATERIALS AND METHODS : From November 2005 to September 2007 , 8 patients ( 5 men and 3 women ) were diagnosed as having metronidazole - induced encephalopathy ( age range ; 43 - 78 years ) .
### Output Text:
MATERIALS AND METHODS : From November 2005 to September 2007 , 8 patients ( 5 men and 3 women ) were diagnosed as having <span class="chemical">metronidazole</span> - induced encephalopathy ( age range ; 43 - 78 years ) . 