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: The patient was taking 80 mg simvastatin at bedtime ( initiated 27 days earlier ) ; amiodarone at a dose of 400 mg daily for 7 days , then 200 mg daily ( initiated 19 days earlier ) ; and 400 mg atazanavir daily ( initiated at least 2 years previously ) .
### Output Text:
The patient was taking 80 mg <span class="chemical">simvastatin</span> at bedtime ( initiated 27 days earlier ) ; <span class="chemical">amiodarone</span> at a dose of 400 mg daily for 7 days , then 200 mg daily ( initiated 19 days earlier ) ; and 400 mg <span class="chemical">atazanavir</span> daily ( initiated at least 2 years previously ) . 