QTc Interval Screening in Methadone Treatment. Ann Intern Med. 2009;150:I-26. doi: 10.7326/0003-4819-150-1-200903170-00104
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Published: Ann Intern Med. 2009;150(6):I-26.
A multidisciplinary panel developed these recommendations. Members of the panel included experts in heart rhythm disturbances (electrophysiologists), pain management and substance abuse specialists, and epidemiologists. The purpose of the panel was to review evidence about adverse effects of methadone on the heart and to develop safety recommendations for doctors prescribing methadone.
Methadone is a synthetic narcotic. It is used to treat opioid addiction and moderate to severe pain. Recent reports suggest that methadone can affect the electrical system of the heart. A heart tracing known as an electrocardiogram (ECG) may detect an abnormality (prolongation of the rate-corrected QT [QTc] interval) in patients treated with methadone. This abnormality can result in a rare but life-threatening heart rhythm problem (arrhythmia) called torsade de pointes.
The panel reviewed and discussed published research, national substance abuse guidelines, and information from regulatory agencies.
The panel found that both oral and intravenous methadone cause QTc interval prolongation and torsade de pointes. Adverse effects of methadone on the heart's electrical system seem to be dose-dependent. How often patients treated with methadone develop arrhythmia is not clear.
Doctors should inform patients of arrhythmia risk when they prescribe methadone. They should ask patients undergoing or considering methadone treatment about any history of heart disease, arrhythmia, and fainting spells. Doctors should check the QTc interval on the patient's ECG before starting methadone treatment, within 30 days after starting treatment, and annually thereafter. If the QTc interval is greater than 450 ms but less than 500 ms, the panel recommends discussing benefits and risks of methadone with the patient and frequent monitoring. If the QTc interval exceeds 500 ms, the panel recommends discontinuing methadone treatment or reducing the methadone dose, eliminating possible contributing factors, or using an alternative therapy. Finally, doctors should be aware of interactions between methadone and other drugs that prolong the QT interval or slow the metabolism of methadone.
The recommendations primarily address safety concerns related to adverse effects of methadone on the heart and do not quantify potential benefits of methadone for particular patient groups. Available evidence was insufficient to estimate the frequency of methadone's adverse effects on the heart.
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