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: Incidence and severity of myalgia did not differ significantly between the two groups : 15 patients in the dexamethasone group complained of myalgia compared with 18 patients in the saline group , and severe myalgia was reported by five patients and three patients , respectively ( not significant ) .
### Output Text:
Incidence and severity of myalgia did not differ significantly between the two groups : 15 patients in the <span class="chemical">dexamethasone</span> group complained of myalgia compared with 18 patients in the saline group , and severe myalgia was reported by five patients and three patients , respectively ( not significant ) . 