1848
While small prospective studies have not revealed any significant drug - drug interaction between warfarin and levofloxacin , several case reports have indicated that levofloxacin may significantly potentiate the anticoagulation effect of warfarin .
 warfarin, levofloxacin, levofloxacin, warfarin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 warfarin, levofloxacin, levofloxacin, warfarin