Impact of methadone treatment on cardiac repolarization and conduction in opioid users

We prospectively assessed the effect of oral methadone on the corrected QT interval (QTc) among 160 patients free of structural heart disease and measured serum methadone concentrations and simultaneous QTc intervals in a subset of 44 participants. Mean ± SD QTc increased by 12.4 ± 23 ms (p <0.001) at 6 months, by 10.7 ± 30 ms (p <0.001) at 12 months, and the QTc change from baseline to 12 months correlated with the trough (r = 0.37, p = 0.008) and peak (r = 0.32, p = 0.03) serum methadone concentrations.