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: CASE SUMMARY : A 41 - year - old Chinese man with a history of hyperthyroidism had been treated with carbimazole and propranolol for the past 5 years .
### Output Text:
CASE SUMMARY : A 41 - year - old Chinese man with a history of hyperthyroidism had been treated with <span class="chemical">carbimazole</span> and <span class="chemical">propranolol</span> for the past 5 years . 