UNLABELLED: Essentials Reversal of anticoagulant effects of dabigatran may occur despite application of idarucizumab. Monitoring of dabigatran level after antidote application is crucial to detect rebound. Repeated doses of idarucizumab may be necessary in cases of massive dabigatran accumulation. Combination of antidote application and renal replacement therapy may offer additional benefit. SUMMARY: Idarucizumab is a monoclonal antibody fragment designed for reversing the anticoagulant effects of dabigatran. Administration is recommended as two intravenous boluses of 2.5 g within 15 min of each other or as a single 5 g bolus. However, in certain situations a second dose of the drug could be necessary. We report the case of a 77-year-old man, treated with dabigatran for paroxysmal atrial fibrillation. He presented at our department with acute renal failure, concomitant massive dabigatran accumulation and subsequent acute gastrointestinal bleeding. Fifty minutes after the administration of idarucizumab, the dabigatran plasma concentration decreased from a peak of 1630 ng ml-1 to a level below the detection limit of 30 ng ml-1 and bleeding stopped. Eight hours after administration, the dabigatran plasma level started to increase up to 1560 ng ml-1 (96% of the maximum value obtained), accompanied by a further drop in hemoglobin. Concomitant hemodialysis and hemofiltration led to a continuous decrease in dabigatran plasma levels. However, sepsis and multiorgan failure ensued, which led to death. With this case report we raise the question of whether massive dabigatran accumulation requires repeated doses of idarucizumab, or alternatively, if the combination of antidote with hemodialysis/renal replacement therapy is advisable in order to remove circulating levels of dabigatran.