• Nasir Mohamad, Muhammad Irfan Abdul Jalal, Azlie Hassan, Muslih Abdulkarim Ibrahim, Roslanuddin Salehuddin, and Nor Hidayah Abu Bakar.
• Nasir Mohamad, MD, MMed, Department of Emergency Medicine, School of Medical Sciences, USM, 16150, Kubang Kerian, Kelantan, Malaysia.
• Pak J Med Sci. 2013 Sep 1; 29 (5): 1132-6.

ObjectivesThis study aimed to compare the QTc interval between low and high dose methadone groups and evaluate the pattern of QTc variation.MethodsThis is a prospective cohort study conducted from December 2010 till August 2011 at Malaysian University of Science's Hospital. Forty six subjects, grouped in high dose (>80mg) and low dose (<80mg) oral methadone, were followed-up at 4-weekly for QTc measurements. Relevant demographic and biochemical profiles were taken at intervals with concurrent QTc measurements.ResultsNo significant QTc differences between methadone dosage groups were found at Week 0 (434ms vs 444ms, p = 0.166) and week 8 (446.5ms vs 459ms, p = 0.076), but not at week 4(435ms vs 450ms, p = 0.029). However, there were significant associations between the groups with QTc prolongation at week 0 and 4 (OR 4.29(95% CI 1.01, 18.72) p=0.044 and OR 5.18 (95% CI 1.34, 20.06) p =0.013, respectively) but not at week 8 (OR 2.44 (95% CI 0.74, 8.01) p=0.139). On multivariate analysis, dose group was the sole significant factor for QTc prolongation for week 0 and 4 (p values 0.047 and 0.017, respectively), but not at week 8.ConclusionHigh-dose methadone group is more likely to develop prolonged QTc than low-dose group. However, such effects were inconsistent and occurred even during chronic methadone therapy, mandating judicious QTc and serum methadone monitoring.

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