Methadone-induced bradycardia

Effect of Methadone or Hydromorphone on Cardiac Conductivity in Dogs Before and During Sevoflurane Anesthesia

Objective: To evaluate changes in electrocardiogram (ECG) variables in healthy dogs receiving either methadone or hydromorphone IV before and during sevoflurane anesthesia.

Study Design: Prospective clinical study.

Animals: Forty client-owned dogs.

Methods: Dogs were randomized to receive methadone 0.5 mg/kg IV or hydromorphone 0.1 mg/kg IV in each part of a two-part study. In part one, dogs received the opioid prior to sevoflurane anesthesia (groups MS, n = 12 and HS, n = 12). Anesthesia was induced with propofol IV, maintained with sevoflurane, and dogs were mechanically ventilated. Standard 6-lead ECG recordings were obtained before opioid administration, 2, 5, and 10 min after opioid administration prior to anesthesia, and during anesthesia 15 min after end-tidal sevoflurane stabilized at 2.4%. In part two, conscious dogs received the same opioid treatments and ECGs were obtained at equivalent time points without undergoing anesthesia (groups M, n = 8 and H, n = 8). Values for ECG variables were determined by a blinded cardiologist and included: Heart rate (HR), PR interval, QT interval, and HR corrected QT interval (QT_c) using the Bazett (QT_cB), Fridericia (QT_cF), and Van de Water (QT_cV) formulas. Differences over time and between all four groups were evaluated using ANOVA for repeated measures with significance set at p ≤ 0.05.

Results: Both methadone and hydromorphone administration reduced HR and prolonged PR and QT intervals, with greater changes observed during sevoflurane anesthesia. The greatest prolongation in QT interval was observed in dogs administered methadone during sevoflurane anesthesia.

Conclusions and Clinical Relevance: Methadone and hydromorphone caused disturbances in myocardial electrical activity, and the addition of sevoflurane enhanced these disturbances. Both drugs caused considerable QT interval prolongation into the proarrhythmogenic range, with methadone causing greater prolongation.

Electrocardiographic Findings in Mortalities Due to Pure Methadone Toxicity

We aimed to evaluate electrocardiographic (ECG) abnormalities in mortalities due to pure methadone toxicity in ICU patients since methadone-related mortality may be due to cardiac complications even in acute toxicities. In a retrospective single-center study, files of all patients who had died with confirmed diagnosis of pure methadone toxicity between 2011 and 2016 were evaluated. Autopsy was performed in all cases. A cardiologist measured all ECG quantitative and qualitative indices. Fifty-one deaths were recorded. Forty-two dead patients were males. Median [IQR] age of the patients was 44 [30, 60] years. Of them, 38 (69%) were methadone-dependent and were significantly older than methadone-naïve patients (p = 0.008 and p = 0.001, respectively). ECG abnormalities were detected in all cases. ST-T abnormalities were found in 33 (64.7%) patients. Except longer PR interval in dependent patients (p = 0.017) and specific ST elevation in naïve cases (p = 0.008), other ECG indices were similar in two groups. No correlation was found between ST-T abnormalities and coronary disease in autopsy. ECG abnormalities irrelevant to coronary artery diseases are common in methadone-related mortalities. Methadone toxicity may affect myocardium and play a role in death. Further prospective studies to evaluate other cardiac indices in methadone-poisoned patients are recommended.

Cardiotoxicity of Oral Methadone as an Analgesic–-Recommendations for Safe Use

Once used only as third-line therapy in the management of chronic pain states, methadone is now being used as first- and second-line therapy. Most risks and the stigma associated with methadone use have been known for years. Only over the past decade or so have the unique pharmacokinetic-pharmacodynamic properties and methods for conversion from other opioids to methadone been established. Pertinent English-language literature was obtained from MEDLINE/PUBMED and EMBASE searches (1966-June 2009). This paper provides an overview of the cardiotoxicity of oral methadone, with an emphasis on its use as an analgesic. Cardiotoxicity during its use in the maintenance of opioid addiction has also been reviewed due to the wealth of epidemiologic, risk factor, and correlative analytic data contained therein. A series of recommendations are provided to improve the cardiac safety profile of oral methadone used for analgesia. In addition, there is a discussion of settings and patient types which may impact upon these recommendations.

QTc Prolongation and Torsades de Pointes Associated with Methadone Therapy

Oral methadone therapy is an effective and increasingly popular treatment for opioid dependency and chronic pain. Although it is not typically considered pro-dysrhythmic, we present the unique case of a 52-year-old HIV-positive woman without underlying cardiac disease who developed QTc prolongation and pulseless Torsades secondary to high dose methadone therapy.