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: After 8 weeks of therapy , in patients whose blood pressure remained uncontrolled , 5 mg amlodipine was added to the initial therapy .
### Output Text:
After 8 weeks of therapy , in patients whose blood pressure remained uncontrolled , 5 mg <span class="chemical">amlodipine</span> was added to the initial therapy . 