ABSTRACT
Introduction: Paroxysmal atrial fibrillation (Paf) occurred in an inpatient who has been prescribed methadone for cancer pain in our palliative care unit, but oral administration of aprindine (antiarrhythmic agent) succeeded in defibrillation and methadone administration could be continued. Case: A 75-year-old man had developed multiple bone metastases after resection of thyroid cancer. Due to refractory cancer pain, switching from oxycodone to methadone was performed. Pain relief was achieved with methadone 40 mg/day and without QT interval prolongation. After methadone administration about 9 months, there suddenly became loss of appetite in the morning of one day. ECG examination revealed Paf onset. Aprindine 20 mg was orally administered for the purpose of defibrillation. After about 2 hours sinus rhythm was gained and later without recurrence. Conclusion: This case was considered to have the coincidental complication of paroxysmal atrial fibrillation in the course of methadone administration. If administration of antiarrhythmic agents is performed in a patient whom has been prescribed methadone, it is feared to lead to result in QT interval prolongation due to drug interactions. It is important to carefully select an agent that rarely leads to QT prolongation.