QT prolongation associated with memantine in A lzheimer's disease

QT prolongation, which can cause torsades de pointes (TdP), by memantine has not yet been reported. We report a case of Alzheimer's disease in which QT prolongation was observed during memantine treatment. The case was a 73-year-old woman who underwent intracardiac catheter intervention 4 years prior due to acute myocardial infarction, and intake of warfarin, aspirin, clopidogrel, furosemide, pitavastatin, lansoprazole, carvedilol, benidipine, spironolactone, trichlormethiazide, potassium supplement, and iron preparations were continued. Renal impairment was also observed following catheter intervention due to the aggravation of chronic heart failure. Memory impairment became prominent, and the patient was admitted to the Psychiatric Department of our hospital. All electrolytes were within normal range at admission; however, renal impairment was observed (serum creatinine = 2.19 mg/dL). Cardiac enlargement, as well as pulmonary congestion was also observed. A mild increase in ST was observed upon electrocardiography and QTc was 438 ms. The patient was diagnosed with Alzheimer's disease, and 5-mg/day memantine was commenced from the 39th hospital day, increased to 10 mg/day on the 45th day, and to 15 mg/day on the 52nd day. On the 57th day, despite a complaint of a sense of discomfort in the chest, no significant change was observed in the QT interval and ST levels. Although the chest discomfort had disappeared, the patient complained once again of chest discomfort when memantine was increased to 20 mg/day on the 59th day; however, no apparent ST change was observed, while QT prolongation of QTc 504 ms was observed, so memantine was immediately reduced and completely discontinued on the 67th day. On the 71st day, QTc changed to 446 ms and no ST increase was observed. During biochemical testing on the 66th hospital day, abnormalities were not observed (serum creatinine = 2.21 mg/dL). Hypokalemia was also not observed. The patient was transferred to another Psychiatric Department for further treatment. The risk for TdP increases when the QTc interval exceeds 500 ms or extends from the baseline by 60 ms;1 therefore, the condition of this case was in a very dangerous state. The present case involved risk factors for QT prolongation, including an old myocardial infarction, congestive heart failure and taking potassium preparations to treat hypokalemia.2 Elderly patients often have several risk factors of QT prolongation; therefore, memantine must be administered very carefully. Dr Someya has received research support and honoraria from Asahi Kasei, Astellas Pharma, Dainippon Sumitomo Pharma, Eisai, Eli Lilly, GlaxoSmithKline, Janssen Pharmaceutical, Kyowa Hakko Kirin, Meiji Seika Pharma, MSD, Novartis Pharma, Otsuka Pharmaceutical, Pfizer Japan, Shionogi, Takeda Pharmaceutical and Yoshitomiyakuhin. Dr Suzuki has received research support and honoraria from Janssen Pharmaceutical, Otsuka Pharmaceutical and Mitsubishi Tanabe Pharma Corporation. The other authors have no conflicts of interest to disclose.