Frequency of prolonged QT intervals in patients treated with methadone referred to an addiction treatment clinic in the north of Iran

Despite the benefits of methadone and its widespread use in opioid treatment programs, this drug has various adverse side effects even at therapeutic doses. This study aimed to determine the frequency of long QT intervals in patients treated with methadone with doses lower than 100 mg.

In this cross-sectional study, all the patients between 30-65 years of age admitted for methadone maintenance treatment were enrolled. A matched group of patients with no history of using methadone was included. Screening electrocardiography was performed for all participants at the beginning. Demographic data, drug history, QT interval, and Maximum QTc time were evaluated. The mean QT interval was compared with the defined normal value using the one sample t-test. Also, the mean QT interval based on the methadone dose consumption and other variables was analyzed using t-test or ANOVA statistical tests. P-value less than 0.05 was considered significant. The statistical analysis was performed using SPSS version 18.

Out of 196 subjects, 97 patients were in the methadone group. 83.5% of methadone users and 68.7% of the control group were males. The mean age was 43.8, and 44.5 in the methadone and control group, respectively. 83.5% of methadone users and 68.7% of the control group were males. In the methadone group, 17.5% had abnormal QTc-Max, while only 2% of the control group had abnormal QTc-Max (P=0.0001). Of the people who consumed less than 40 mg of methadone daily, 3.7%, and those who consumed more than 40 mg, 34.9% experienced abnormal QTc-Max (P=0.0001). This survey revealed that methadone use in even doses lower than 100 mg could also increase the risk of QT prolongation. Therefore, the treatment team needs to be aware that arrhythmias might occur within a wide range of methadone treatment doses.