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: Alteplase was discontinued , and the patient was reinitiated on argatroban ; ultimately , he was transitioned to warfarin for long - term anticoagulation .
### Output Text:
Alteplase was discontinued , and the patient was reinitiated on <span class="chemical">argatroban</span> ; ultimately , he was transitioned to <span class="chemical">warfarin</span> for long - term anticoagulation . 