Effect of amphetamine on corrected-QT interval change during methadone maintenance treatment in Taiwan: A prospective cohort study

Introduction and Aims: Previous studies have suggested that methadone is associated with prolonged corrected-QT (QTc) interval, but published prospective research studies in this area are relatively scarce. This study investigates QTc interval change among methadone maintenance patients and possible associated risk factors. One of the aims is to explore the effect of amphetamines. Design and Methods: This prospective cohort study with six-month follow up assesses the effect of methadone on QTc interval among a sample (n=170) of heroin users in a methadone maintenance treatment program in Taiwan. Demographic data, substance use history, medical history and laboratory studies were collected at study enrollment. Twelve-lead electrocardiograms were performed for all participants both at study enrollment and six months later. Results: The median daily methadone dose was 41mg. A mean increase of QTc interval (17.1ms, SD=50.0, P<0.001) was found at six-month follow up. QTc interval prolongation in the sample at baseline was 2.9%, and at six months was 12.4%. A positive correlation was found between comorbid amphetamine use frequency in the past month and QTc interval change. Methadone dose was not associated with QTc change. Discussion and Conclusions: An increase of mean QTc interval was found among methadone maintenance patients at six-month follow up. Electrocardiogram monitoring should be performed among patients who are at risk of frequently using amphetamines during methadone maintenance treatment.