Methadone: QT interval

Pharmacology

There is an FDA Black Box Warning  on methadone which states, In addition, cases of QT interval prolongation and serious arrhythmia (torsades de points) have been observed during treatment with methadone. Most cases involve patents being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction

An independent advisory panel to the FDA recommended pretreatment ECG, followed by a follow up at 30 days and then annually, although the panel recommended more  frequent ECG monitoring for doses in excess of 100 mg/day or if QTc > 450 ms

Methadone and QT Interval (FDA BLACK BOX)

  • Background: has caused QT prolongation and torsades . Sudden death reported in doses as low as 20 mg/day
  • Etiology: inhibitor of human cardiac ether-a-go-go-related gene (hERG) , which encodes Ikr (delayed rectifier inward potassium channel)
  • Confounding Factors: history of long QT syndrome or sudden cardiac death in the patient or family, other rhythm disturbances, structural heart disease, CPY inhibitors, other QT prolonging drugs
  • Monitoring: pretreatment ECG, follow up at 30 days and then annually (more frequent for doses in excess of 100 mg/day or if QTc > 450 ms)

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2011

Year asked