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: METHODS : One hundred sixty - eight adult outpatients with mild to moderate hypertension were randomly allocated in double - blind fashion and equal number to receive 80 mg valsartan or 5 mg amlodipine for 12 weeks .
### Output Text:
METHODS : One hundred sixty - eight adult outpatients with mild to moderate hypertension were randomly allocated in double - blind fashion and equal number to receive 80 mg <span class="chemical">valsartan</span> or 5 mg <span class="chemical">amlodipine</span> for 12 weeks . 