[Can acute renal insufficiency increase the effect of warfarin?].

The use of warfarin is complicated by its narrow therapeutic index. The risk of severe complications in the form of haemorrhage is significantly increased by an elevated degree of anticoagulation. We present a case in which a patient in stable warfarin treatment was admitted with acute renal failure and extremely high international normalized ratio (INR). No single mechanism can fully explain this. We find that it was probably caused by accumulation of active metabolites, an inhibitory factor in uraemic blood, which reduces hepatic metabolism and a genotype with an unstable metabolism of warfarin.