title: Hemarthrosis in a patient on warfarin receiving ceftaroline: a case report and brief review of cephalosporin interactions with warfarin.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  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.
authors: Department of Clinical Pharmacy and Outcomes Sciences, College of Pharmacy, Medical University of South Carolina, Charleston, USA. bohm@musc.edu
authors: Nicole M
authors: NM
authors: Bohm
authors: Brittany
authors: B
authors: Crosby
mesh_terms: D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000009:adverse effects*; D000925:Anticoagulants / Q000009:adverse effects*; D002481:Cellulitis / Q000188:drug therapy / Q000503:physiopathology; D002511:Cephalosporins / Q000009:adverse effects*; D004347:Drug Interactions; D005260:Female; D006395:Hemarthrosis / Q000139:chemically induced* / Q000503:physiopathology; D006801:Humans; D019934:International Normalized Ratio; D014859:Warfarin / Q000009:adverse effects*; D000097583:Ceftaroline
chemical_list: D000900:Anti-Bacterial Agents; D000925:Anticoagulants; D002511:Cephalosporins; D014859:Warfarin; D000097583:Ceftaroline