Fidaxomicin Use for Clostridium Difficile Infection Probably Decreases the Effect of Coumadin® in Elderly

The incidence of Clostridium difficile infection (CDI) has been decreasing in the last decade, though the incidence of community-acquired CDI has remained stable. In an elderly patient on Coumadin®, we report an unexpected decrease in international normalized ratio (INR) during the treatment of second recurrence of CDI treated with fidaxomicin. According to the available information, fidaxomicin does not interfere with warfarin. However, in this case, warfarin effects diminished, and only with increased dosage therapeutic INR was achieved.