Ceftriaxone Potentiates Warfarin Activity Greater Than Other Antibiotics in the Treatment of Urinary Tract Infections

<p> <p id="x-x-p-1"> <strong> Background: </strong> The cephalosporin class has been associated with an increased risk of bleeding among elderly patients receiving warfarin. Urinary tract infections (UTI) are the most prevalent infection in elderly patients. <p id="x-x-p-2"> <strong> Objective: </strong> To determine the extent of interaction between antibiotics used in the treatment of UTI, particularly specific cephalosporins and warfarin. <p id="x-x-p-3"> <strong> Methods: </strong> A retrospective chart review was conducted on chronic warfarin patients with a diagnosis of UTI treated with ceftriaxone, a first-generation cephalosporin, penicillin, or ciprofloxacin. The primary outcome was the comparison of the extent of international normalized ratio (INR) change from baseline between each antibiotic group. <p id="x-x-p-4"> <strong> Results: </strong> The ceftriaxone group was found to have a statistically significant higher peak INR value compared to all other studied antibiotics (ceftriaxone: 3.56, first-generation cephalosporins: 2.66, penicillins: 2.98, ciprofloxacin: 2.3; <em> P </em> = .004), a statistically significant greater extent of change in INR value (+1.19, +0.66, +0.8, +0.275; <em> P </em> = .006), and a statistically significant greater percentage change in INR value when compared to ciprofloxacin (54.4% vs 12.7%; <em> P </em> = .037). <p id="x-x-p-5"> <strong> Conclusion: </strong> Ceftriaxone interacts with warfarin to increase a patient&rsquo;s INR value more than other commonly administered antibiotics for UTI treatment. Other antibiotics should be preferred for UTI treatment in patients on warfarin. </p> </p> </p> </p> </p></p>