Measurement of QTc in patients receiving chronic methadone therapy

Recent reports suggest that methadone may prolong the QTc interval and cause torsades de pointes. This study was conducted to evaluate the prevalence of QTc Prolongation, during oral nwhadone therapy and iidentify factors associated with prolongation. Patients receiving oral methadone as treatment for chronic pain or addiction were eligible for the study. One hundred four patients who were receiving >= 20 mg methadone per day for >= 2 weeks underwent. electrocardiograms to measure QTc interval duration. Sixty-three (61 %) patients were male and 63 (61 %) were receiving methadone maintenance fior opioid addiction). The nzean (+/- SD) age was 45.3 +/- 9.4 years. The median (range) methadone dose was 110 mg/day (20-1200 mg/day); median (range) number of months on methadone was 12.5 inonths (1-444 months). The median, (range) QTc interval was 428 msec (396-494 msec). Thirty-three percent had QTc prolongation (males 40 %, females 20 %; P = 0.03). No patient, had a QTc longer than 500 msec. Significant dose response was observed in niain males methadone < 12 inonths (rho = 0.60, P = 0.02). Our study suggests that methadone prolong the QTc interval in specific subpopulations but poses little risk of serious prolongation.. J Pain Symptom Manage 2005;29:385-391. (c) 2005 U.S. Cancer Pain Relief Committee. Published by Elsevier Inc. All rights reserved.