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: Argatroban has no specific antidote , and if excessive anticoagulation occurs , argatroban infusion should be stopped or reduced .
### Output Text:
<span class="chemical">Argatroban</span> has no specific antidote , and if excessive anticoagulation occurs , <span class="chemical">argatroban</span> infusion should be stopped or reduced . 