Sudden cardiac arrest in a patient on chronic methadone after the addition of azithromycin.

Corrected QT-interval (QTc) prolongation with increased risk of fatal arrhythmia is a well-established toxicity of methadone. In this study, a case of sudden cardiac arrest in a patient on chronic methadone therapy is presented. A 47-year-old man presented unresponsive to the emergency department after pulseless arrest at his home. The patient's wife revealed he was taking methadone as part of an ongoing opioid dependency treatment and that he was prescribed azithromycin for an upper respiratory tract infection 3 days before his presentation. A 12-lead electrocardiogram at the time of presentation showed sinus tachycardia and a QTc of 490 milliseconds. It was concluded that the patient experienced a fatal arrhythmia because of QTc prolongation, precipitated by azithromycin in the setting of ongoing methadone use.