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美國食物及藥物管理局(USFDA)收到關於使用citalopram後出現QT間期延長和尖端扭轉心律失常(Torsade de Pointes)的上市後報告, 相對於安慰劑, 服用20mg和60mg citalopram的病人在個體化修正後的QT間期分別延長了平均最多8.5和18.5毫秒(milliseconds)。過往, citalopram的指引建議某些病人可能需要每天60mg的劑量, 但研究並未顯示每天使用高於40mg的劑量可更有效地治療抑鬱症。因已確認citalopram會引起劑量依賴性的QT間期延長, 因此, 請醫生﹑藥劑師及其他衛生專業人士注意：
- 建議不應使用每天高於40mg的劑量, 亦不應對患有先天性QT間期延長的病人使用citalopram；
- 患有充血性心力衰竭﹑心律緩慢或因同時患有其他疾病或併用藥物而較易發生低血鉀或低血鎂的病人, 出現尖端扭轉心律失常的風險較高；
- 於開始使用citalopram前, 應糾正病人倘有的低血鉀和低血鎂狀況, 並根據相應的臨床情況監測病人的電解質水平；
- 對於患有充血性心力衰竭﹑心律緩慢或併用可延長QT間期藥物的病人, 考慮更頻密地監測病人的心電圖；
- 因為肝功能受損﹑60歲以上﹑CYP2C19慢代謝型或併用cimetidine的病人, 血中citalopram的濃度會上升, 增加QT間期延長和尖端扭轉心律失常的風險, 因此對於這類病人, 最大的建議劑量是每天20mg；
- 對輕至中度腎功能受損的病人, 不需調整劑量；
- 建議服用citalopram的病人如出現不正常的心跳或心率, 應立即向醫生求診。
United Food and Drug Administration (USFDA) has received post-marketing reports of QT interval prolongation and Torsade de Pointes associated with Citalopram. Compared to placebo, maximum mean prolongations in the individually corrected QT intervals were 8.5 and 18.5 milliseconds (ms) for 20 mg and 60 mg citalopram, respectively. Previously, guidelines of citalopram indicated that certain patients may require a dose of 60 mg per day. Studies did not show a benefit in the treatment of depression at doses higher than 40 mg per day. Since it has been demonstrated that citalopram causes dose-dependent QT interval prolongation, therefore, it is recommended that physicians, pharmacists and healthcare professionals:
- citalopram should no longer be used at doses above 40 mg per day or be used in patients with congenital long QT syndrome;
- patients with congestive heart failure, bradyarrhythmias, or predisposition to hypokalemia or hypomagnesemia because of concomitant illness or drugs, are at higher risk of developing Torsade de Pointes;
- hypokalemia and hypomagnesemia should be corrected before administering citalopram. Electrolytes should be monitored as clinically indicated;
- more frequent electrocardiogram (ECG) monitoring in patients with congestive heart failure, bradyarrhythmias, or patients on concomitant medications that prolong the QT interval should be considered;
- 20 mg per day is the maximum recommended dose for patients with hepatic impairment, who are greater than 60 years of age, who are CYP 2C19 poor metabolizers, or who are taking concomitant cimetidine, because these factors increase blood levels of citalopram and the risk of QT interval prolongation and Torsade de Pointes;
- no dose adjustment is necessary for patients with mild or moderate renal impairment;
- patients should be advised to contact a physician immediately if they experience signs and symptoms of an abnormal heart rate or rhythm while taking citalopram.
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