Maxifloxacin and Warfarin

Publication Date: 
Tue, 11/08/2011
By: Alere Staff

Moxifloxacin is in a class of antibiotics called fluoroquinolones and is used to treat certain infections. A June 2005 report in Pharmacotherapy reported increases in INR values in previously stable patients among those initiating moxifloxacin.1

Several case reports have been published regarding an interaction between fluoroquinolones and warfarin; however, the exact mechanism of the interaction has yet to be established. Three patients received warfarin and experienced increases in international normalized ratio (INR) when moxifloxacin was added. Two of the patients had stable anticoagulation regimens and then experienced persistent elevations in their INRs shortly after therapy with moxifloxacin was started. The third patient experienced a dramatic rise in INR after the first dose of moxifloxacin was administered.

The cases presented in Pharmacotherapy strengthen the evidence thatan interaction does exist despite manufacturer-generated statements to the contrary. Increased awareness of this potential interaction is necessary to ensure appropriate monitoring and improve therapeutic decision-making.

  1. Arnold LM, Nissen LR, Ng TM. Moxifloxacin and warfarin: additional evidence for a clinically relevant interaction. Pharmacotherapy. 2005 Jun;25(6):904-7.