[Marked PT-INR prolongation associated with appetite loss due to urinary tract infection in a late elderly case with chronic atrial fibrillation].

An 80-year old woman presented with macroscopic hematuria on June 4(th), 2008. She had been suffering from general malaise and appetite loss since about 10 days previously. She had received anticoagulant therapy with warfarin due to chronic atrial fibrillation and PT-INR was well controlled between 1.6-2.2. When she presented, PT-INR was 12.88, and urinary tract infection (UTI) and hypoalbuminemia (2.2 g/dl) were observed. Therefore, warfarin therapy was discontinued, and antibiotics and vitamin K were administered. Normalization of PT-INR resulted in the disappearance of hematuria and UTI improved as a result of antibiotics administration. As the appetite loss improved, for serum albumin level increased. The previous dose of warfarin achieved PT-INR around 1.8. Her drug compliance had been good, and she took no drug nor food which could interact with warfarin. We also found no liver dysfunction, acute renal failure, malignancy, nor hyper- or hypo-thyroidism. Hypoalbuminemia caused by appetite loss due to UTI seems very likely to increase concentration of circulating free warfarin resulting in extreme prolongation of PT-INR. Our findings in the present case may suggest that we should pay more attention on changes of drug pharmacokinetics in elderly patients because of their poor adaptation to their circumstances such as infection or dehydration.