Consequences of cardiac toxicity in patients on low methadone doses during methadone maintenance treatment

Abstract

© 2015 Pacini Editore S.p.A. All rights reserved. Background. Methadone has been extensively studied and prescribed worldwide in the methadone maintenance treatment (MMT) of opiate addicts. However, methadone-induced prolongation of the corrected QT (QTc) interval has been reported, and it could be associated with torsades de pointes (TdP). In cases of more persistent TdP, ventricular fibrillation leading to cardiac arrest and sudden death could develop. Aim. We report the consequences of cardiac toxicity in two patients who were receiving low doses of methadone (≤ 60 mg), along with diazepam as the main adjunctive therapy. Surprisingly, one patient developed malignant arrhythmia and the other one died at the very start of MMT. Case Presentations. A 28-year-old male died at the very start of MMT while receiving low doses of methadone (30 mg/day), diazepam (30 mg) and clozapine (25 mg). The forensic pathologist who reported his death classified it as being methadone-related, with signs of acute lung oedema of cardiac origin and myocardial changes. A 37-year-old male on a low methadone dose (60 mg/day) and diazepam (30 mg) developed significant QTc prolongation and malignant arrhythmia during triple antibiotic therapy (gentamicin, ceftriaxone, metronidazole) of phlegmon of the lower limb. After treatment at the Intensive Care Unit and the discontinuation of methadone and diazepam, a regular cardiac function was restored. Conclusions. It is highly advisable for health care professionals to be cautious in prescribing benzodiazepines and other drugs, even when patients are on low MMT doses. Significant QTc prolongation, followed by the development of potentially fatal arrhythmia in opiate addicts on low-dose MMT is more likely to occur when several concomitant factors are acting simultaneously.