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: Its antiarrhythmic effectiveness surpasses that of propranolol and pindolol inhibiting the ouabain arrhythmia in dogs and cats .
### Output Text:
Its antiarrhythmic effectiveness surpasses that of <span class="chemical">propranolol</span> and <span class="chemical">pindolol</span> inhibiting the <span class="chemical">ouabain</span> arrhythmia in dogs and cats . 