Methadone, a pharmacological agent used to treat heroin dependence is relatively safe, but may cause cardiac arrhythmias in the concurrent presence of other risk factors. APPROACH AND KEY FINDINGS: This case report highlights the risk of torsade de pointes, a life-threatening cardiac arrhythmia, in a heroin-dependent patient receiving methadone substitution therapy who was prescribed itraconazole for vaginal thrush. The patient presented to the accident and emergency department for chest discomfort and an episode of syncope following two doses of itraconazole (200 mg). Electrocardiogram monitoring at the accident and emergency department showed prolonged rate-corrected QT interval leading to torsade de pointes. The patient was admitted for cardiac monitoring, and electrocardiogram returned to normal upon discontinuation of methadone.
Matched MeSH terms: Torsades de Pointes/chemically induced*; Torsades de Pointes/diagnosis*; Torsades de Pointes/physiopathology
A 68-year-old diabetic and hypertensive woman presented with chronic autonomic diarrhoea, syncope and palpitations which were associated with QT prolongation and recurrent episodes of torsade de pointes. She was on glibenclamide, indapamide and probucol (for type V hyperlipidaemia). Despite intravenous infusions of potassium, lignocaine and amiodarone, the unstable rhythm persisted. However, intravenous magnesium sulphate with small doses of intravenous propranolol terminated the torsade de pointes. She was stabilised but following discharge she relapsed, and upon re-admission, succumbed to intractable ventricular fibrillation. Early recognition and aggressive treatment of this condition is emphasised. Multiple aggravating factors ie autonomic diarrhoea resulting in severe potassium and magnesium depletion, kaliuretic effect of indapamide, probable QT prolongation associated with diabetic autonomic neuropathy and probucol; probable underlying coronary artery disease and heightened emotional and sympathetic discharge could have contributed to this very unstable ventricular arrhythmia and sudden death.
Matched MeSH terms: Torsades de Pointes/complications*
Objective: This case report highlights the risk of Torsade de Pointes (TdP), a life threatening cardiac arrhythmia in a heroin dependent patient receiving methadone substitution therapy who was prescribed erythromycin for upper respiratory tract infection. Method: We report a case of a 35-year-old Malay man on methadone maintenance treatment who developed TdP possibly due to drug interaction between methadone and erythromycin. Results: The
patient reported feeling unwell, chest pain and feeling dizzy after consuming 2 doses of erythromycin. ECG monitoring showed prolonged rate-corrected QT interval leading to TdP. The patient was admitted to the ward where the cardiac arrhythmia ceased following methadone discontinuation. This cardiac arrhythmia was most likely due to drug interaction between methadone and erythromycin (an enzyme inhibitor) which led to an increase in methadone concentration and potentiated the adverse effects. Conclusion: As methadone is a beneficial treatment for heroin dependent patients, the risk of cardiac arrhythmia is of great concern. To avoid complications of drug interaction, patients on methadone therapy should be advised to seek medical assessment before taking other drugs. As TdP is life threatening, it is thus important that physicians and psychiatrists involved in the treatment of
heroin dependent patients on methadone substitution therapy be made aware of this risk.