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To the Editor: In their article about the QT interval, Dr Al-Khatib and colleagues¹ described the propensity of a number of drugs for causing QT prolongation. The authors categorized the synthetic opioid methadone as an "improbable" agent regarding its potential to delay repolarization. Their review, however, was based on an expert panel discussion from August 2000. Since that time, a number of new findings have emerged that, taken together, suggest that an association between methadone and QT prolongation can no longer be considered "improbable."

Recently, a series of 17 methadone-treated patients experiencing torsade de pointes was described.² Subsequently, in an experimental model methadone was found to inhibit the delayed rectifier potassium ion current (IK_r), a plausible mechanism for arrhythmia.³ In this model, methadone was 100 times more potent an inhibitor of IK_r than morphine, a naturally occurring opioid. Preliminary electrocardiographic (ECG) data suggested that methadone induction can increase the . . . [Full Text of this Article]

Mori J. Krantz, MD
Cardiology Division
University of Colorado
Denver

Bridget A. Martell, MD; Julia H. Arnsten, MD, MPH; Marc N. Gourevitch, MD, MPH
Montefiore Medical Center
Albert Einstein College of Medicine
Bronx, NY

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