We commend Wedam et al1 for their addition to the medical literature regarding the prolongation of the rate-corrected QT (QTc) interval associated with opioid pharmacotherapy. Although the effect of methadone on cardiac repolarization has been documented in a prospective cohort study,2 the study by Wedam et al1 is the first randomized trial to our knowledge that compares the impact of levomethadyl acetate, methadone hydrochloride, and buprenorphine hydrochloride on the QTc interval. It is now clear that substantial QTc interval prolongation with methadone may be fairly common, since the authors observed that 23% of methadone-treated subjects with a normal QTc interval at baseline developed QTc prolongation during treatment. The comparatively lower risk of QTc prolongation with buprenorphine is consistent with its lower potency in blocking the cardiac delayed rectifier potassium ion channel.
Baker WA, Krantz MJ. QTc Interval Prolongation and Opioid Addiction Therapy. Arch Intern Med. 2008;168(14):1592. doi:10.1001/archinte.168.14.1592