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: A score of 7 on the Naranjo adverse drug reaction probability scale indicates a probable relationship between the patient ' s sinus bradycardia and the drug interaction between metoprolol and terbinafine .
### Output Text:
A score of 7 on the Naranjo adverse drug reaction probability scale indicates a probable relationship between the patient ' s sinus bradycardia and the drug interaction between <span class="chemical">metoprolol</span> and <span class="chemical">terbinafine</span> . 