Warfarin Interactions With Antibiotics in the Ambulatory Care Setting

Study Questions:

What is the impact of co-prescription of antibiotics for acute respiratory tract infection to patients receiving long-term warfarin therapy on clinically significant international normalized ratio (INR) increases, compared to patients receiving long-term warfarin therapy who are not ill (stable controls) and those who are acutely ill, but not receiving concomitant antibiotics (sick controls)?