Hemarthrosis in a Patient on Warfarin Receiving Ceftaroline: A Case Report and Brief Review of Cephalosporin Interactions with Warfarin

Abstract

To report a possible interaction between warfarin and ceftaroline, resulting in hemarthrosis, and provide readers with an understanding of mechanisms of interaction between cephalosporins and warfarin. Ceftaroline was prescribed for an 85-year-old female with a therapeutic international normalized ratio (INR) hospitalized for the treatment of cellulitis. She was subsequently readmitted with shoulder pain and a supratherapeutic INR. The patient was diagnosed with hemarthrosis, presumably related to elevated INR. Evaluation using the drug interaction probability scale for warfarin and ceftaroline yielded a score consistent with a possible or probable interaction. Cephalosporins may interact with warfarin through a variety of mechanisms, including potentiation of hypoprothrombinemia related to certain side chain groups, inhibition of P-glycoprotein, or alteration of gastrointestinal flora. All mechanisms reported in the medical literature as of April 2012 are briefly examined, but the latter is the most reasonable mechanism for a ceftaroline interaction with warfarin. Health care providers should consider closely monitoring patients receiving antibiotics with activity against Enterobacteriaceae and warfarin, even if no direct mechanism of interaction has been reported. Further research regarding a ceftaroline-warfarin interaction is warranted.