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: Short - and intermediate - term treatment with therapeutic ( 10 or 20 mg daily ) and supratherapeutic ( 40 or 80 mg daily ) valdecoxib doses was not associated with an increased incidence of thrombotic events relative to nonselective NSAIDs or placebo in osteoarthritis and rheumatoid arthritis patients in controlled clinical trials .
### Output Text:
Short - and intermediate - term treatment with therapeutic ( 10 or 20 mg daily ) and supratherapeutic ( 40 or 80 mg daily ) <span class="chemical">valdecoxib</span> doses was not associated with an increased incidence of thrombotic events relative to nonselective NSAIDs or placebo in osteoarthritis and rheumatoid arthritis patients in controlled clinical trials . 