Association Between the Prothrombin Time-International Normalized Ratio and Concomitant Use of Antibiotics in Warfarin Users: Focus on Type of Antibiotic and Susceptibility of Bacteroides fragilis to Antibiotics.

Concomitant use of FQs, or of antibiotics to which B fragilis is susceptible is associated with higher risk of excessive anticoagulation. These findings would contribute to safe and proper antibiotic treatment in warfarin users.