QT PROLONGATION AND VENTRICULAR ARRHYTHMIA IN METHADONE USER PRESENTING WITH SEVERE HYPOKALEMIA
Keywords:
Hypokalemia, QT prolongation, methadone, arrhythmiaAbstract
Introduction: Severe hypokalemia is a serious, life-threatening condition that can lead to muscle
weakness, paralysis, fatigue and different types of cardiac rhythm disturbances including QT prolongation and
furthermore lethal arrhythmias. On the other hand, prolongation of the QT interval can be exacerbated in methadone
users who receive high doses of the drug. Methadone is a drug that is mostly used as a replacement therapy for
opiates, and it is known that it can interfere in the cardiac action potential cycle.
Case report: We present a case of 39y/old male who visited our clinic brought by an ambulance due to palpitations,
fatigue and muscle weakness in the arms and legs. The patients’ symptoms aggravated in the past 2 weeks when he
lost the ability to do the everyday activities and finally to walk, because of extreme weakness of the extremities. On
the day of the admission, he experienced a syncope for the first time in his life. His initial ECG revealed sinus
rhythm with prolonged QT interval and polymorphic ventricular extrasystoles, which evolved in nonsustained
ventricular tachycardia. His initial laboratory finding showed severe hypokalemia, and his previous medical history
revealed use of methadone replacement therapy for approximately 20 years. The patient was closely monitored in
the intensive care unit, and potassium replacement therapy was immediately initiated by the use of intravenous
potassium infusion. Toxicologist and nephrologist were also included in the treatment in order to reduce the
methadone dose and to exclude a secondary cause of severe hypokalemia. The patient’s condition improved after 9
days, when the potassium level was in normal range and the rhythm disturbances completely resolved.
Conclusion: This case highlights the importance of timely recognition of severe electrolytic abnormalities that can
lead to dangerous arrhythmias. Careful replacement with 24h monitoring and frequent laboratory analysis is required
until the potassium level reaches the target range and until the heart rhythm stabilizes.
This case also reveals the importance of the significance of the follow up of every drug addict that receives
methadone replacement therapy on a primary level, in order to exclude QT prolongation. In these cases, the dose of
methadone should be reduced or replaced with another medication, in order to prevent potentially lethal arrhythmias.
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