The physician should inform the patient of the risks of methadone therapy, including cardiac arrhythmias.
The physician should identify risk factors for a prolonged QTc prior to starting methadone therapy:
(1) history of structural heart disease
(2) history of syncope
(3) history of cardiac arrhythmias
(4) family history of cardiac arrhythmias
(5) medications that may prolong the QTc or reduce elimination of methadone
Indications for monitoring the patient's ECG:
(1) pretreatment (to detect pre-existing QTc prolongation)
(2) within 30 days of starting methadone therapy
(3) annually
(4) methadone dose > 100 mg/day
(5) unexplained syncope or seizures
(6) prolongation of QTc
(7) starting a medication that prolongs QTc or reduces methadone elimination
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QTc (milliseconds)
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Response
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451 to 499 ms
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discuss risks vs benefits with the patient; monitor ECG more frequently
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>= 500 ms
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consider reducing dose or discontinuing therapy; try to eliminate contributing factors; consider an alternative therapy
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