Torsades de pointes and self-terminating ventricular fibrillation in a prescription methadone user

Short-acting versus long-acting opioids for pediatric postoperative pain management

INTRODUCTION

Opioids are potent analgesics commonly used to manage children's moderate to severe perioperative pain in children. A wide range of short and long-acting opioids are used to treat surgical pain and will be reviewed in this article.

AREAS COVERED

Both short- and long-acting opioids contain unique therapeutic benefits and adverse effects; however, due to the side effect profile and safety concerns, lack of familiarity, and evidence with long-acting opioids to treat surgical pain, shorter-acting opioids have traditionally been used in children. Almost all opioids work by binding to the mu receptor. Methadone, a long-acting opioid, is an exception because it also has beneficial N-methyl-D-aspartate antagonist properties. Clinically methadone's properties could translate to improved analgesic outcomes, reduced risk of adverse events, less risk for acute hyperalgesia, tolerance and abuse potential, faster recovery, and reduced risk for chronic persistent surgical pain. This review article summarizes and compares the evidence of commonly used short and long-acting opioids for perioperative pain control in the pediatric population.

EXPERT OPINION

Individualized methadone therapy using pharmacogenomics has the potential to transform opioid use in pain management by improving patient safety and analgesic outcomes, thereby addressing the gaps in current standardized ERAS protocols.

Methadone: applications in pediatric anesthesiology and critical care medicine

Like morphine, methadone is a pure agonist at the µ opioid receptor. However, in distinction to morphine which has an elimination half-life of 2-3 h, methadone has an elimination half-life of 24-36 h. In addition to its effects at the µ opioid receptor, methadone is an antagonist at the N-methyl-D-aspartate (NMDA) receptor and also inhibits the reuptake of the neurotransmitters, serotonin and norepinephrine, in the central nervous system. Given its long half-life and high oral bioavailability, methadone has had a primary role in the outpatient treatment of patients with a history of opioid abuse or addiction. However, its unique pharmacology and cellular effects make it a valuable agent in the treatment of both acute and chronic pain of various etiologies. The following manuscript reviews the pharmacologic properties of methadone and discusses its clinical applications in the practice of pediatric anesthesiology and pediatric critical care medicine.

A systematic review of the cardiotoxicity of methadone

Methadone is one of the most popular synthetic opioids in the world with some favorable properties making it useful both in the treatment of moderate to severe pain and for opioid addiction. Increased use of methadone has resulted in an increased prevalence of its toxicity, one aspect of which is cardiotoxicity. In this paper, we review the effects of methadone on the heart as well as cardiac concerns in some special situations such as pregnancy and childhood.

METHODS

We searched for the terms methadone, toxicity, poisoning, cardiotoxicity, heart, dysrhythmia, arrhythmia, QT interval prolongation, torsade de pointes, and Electrocardiogram (ECG) in bibliographical databases including TUMS digital library, PubMed, Scopus, and Google Scholar. This review includes relevant articles published between 2000 and 2013. The main cardiac effects of methadone include prolongation of QT interval and torsade de pointes. Other effects include changes in QT dispersion, pathological U waves, Taku-Tsubo syndrome (stress cardiomyopathy), Brugada-like syndrome, and coronary artery diseases. The aim of this paper is to inform physicians and health care staff about these adverse effects. Effectiveness of methadone in the treatment of pain and addiction should be weighed against these adverse effects and physicians should consider the ways to lessen such undesirable effects. This article presents some recommendations to prevent heart toxicity in methadone users.

Opioid side effects and their treatment in patients with chronic cancer and noncancer pain

Opioids are the foundation of standard analgesic regimens for moderate to severe pain due to life-threatening illnesses such as cancer, and are increasingly employed in chronic noncancer pain of the same severity. Opioids are frequently used for long periods in these populations, sometimes for years. However, side effects are common and may reduce quality of life, or become life threatening, and frequently cause patients to discontinue opioid therapy. Successful opioid therapy dictates that benefits of analgesia outweigh safety concerns. The mechanisms, incidence, and treatment or prevention of commonly reported side effects in chronic pain populations are reviewed, employing best available evidence along with empiric practice. General management strategies include switching opioids ("opioid rotation"), discontinuation of concurrent medications that exacerbate side effects, and symptomatic treatment. In addition, recently recognized adverse events that occur after long-term opioid therapy are discussed. High-quality evidence is lacking for the treatment of most side effects, and the true incidence, underlying mechanisms, and clinical implications of long-term responses to opioid therapy are not yet fully understood.

QT interval screening in methadone maintenance treatment: report of a SAMHSA expert panel

In an effort to enhance patient safety in opioid treatment programs, the Substance Abuse and Mental Health Saervices Administration convened a multi-disciplinary Expert Panel on the Cardiac Effects of Methadone. Panel members (Appendix A) reviewed the literature, regulatory actions, professional guidances, and opioid treatment program experiences regarding adverse cardiac events associated with methadone. The Panel concluded that, to the extent possible, every opioid treatment program should have a universal Cardiac Risk Management Plan (incorporating clinical assessment, electrocardiogram assessment, risk stratification, and prevention of drug interactions) for all patients and should strongly consider patient-specific risk minimization strategies (such as careful patient monitoring, obtaining electrocardiograms as indicated by a particular patient's risk profile, and adjusting the methadone dose as needed) for patients with identified risk factors for adverse cardiac events. The Panel also suggested specific modifications to informed consent documents, patient education, staff education, and methadone protocols.

Opioid pharmacotherapy for chronic non-cancer pain in the United States: a research guideline for developing an evidence-base

This document reports the consensus of an interdisciplinary panel of research and clinical experts charged with reviewing the use of opioids for chronic noncancer pain (CNCP) and formulating guidelines for future research. Prescribing opioids for chronic noncancer pain has recently escalated in the United States. Contrasting with increasing opioid use are: 1) The lack of evidence supporting long-term effectiveness; 2) Escalating misuse of prescription opioids including abuse and diversion; and 3) Uncertainty about the incidence and clinical salience of multiple, poorly characterized adverse drug events (ADEs) including endocrine dysfunction, immunosuppression and infectious disease, opioid-induced hyperalgesia and xerostomia, overdose, falls and fractures, and psychosocial complications. Chief among the limitations of current evidence are: 1) Sparse evidence on long-term opioid effectiveness in chronic pain patients due to the short-term time frame of clinical trials; 2) Insufficiently comprehensive outcome assessment; and 3) Incomplete identification and quantification of ADEs. The panel called for a strategic interdisciplinary approach to the problem domain in which basic scientists and clinicians cooperate to resolve urgent issues and generate a comprehensive evidence base. It offered 4 recommendations in 3 areas: 1) A research strategy for studying the effectiveness of long-term opioid pharmacotherapy; 2) Improvements in evidence-generation methodology; and 3) Potential research topics for generating new evidence.

PERSPECTIVE

Prescribing opioids for CNCP has outpaced the growth of scientific evidence bearing on the benefits and harms of these interventions. The need for a strong evidence base is urgent. This guideline offers a strategic approach to creating a comprehensive evidence base to guide safe and effective management of CNCP.

Torsades de pointes associated with methadone and voriconazole

This report concerns a case of torsades de pointes (TdP) associated with the concomitant administration of methadone and voriconazole in a patient with comorbid medical conditions. A 57-year-old man, with a medical history of human immunodeficiency virus, infective endocarditis, hepatitis C and orbital Aspergillus infection, was admitted to the intensive care unit following several episodes of TdP. The patient was being treated with methadone for opioid addiction and had started taking voriconazole 2 weeks prior for orbital Aspergillosis. He experienced multiple episodes of TdP with a prolonged QTc interval (>600 ms). The pronounced inhibitory impact of voriconazole on methadone metabolism via the cytochrome P450 (CYP)2B6 isoenzyme was identified as a probable cause of the arrhythmia. Voriconazole was subsequently temporarily withheld and the methadone dose was significantly reduced. The patient received an implantable cardioverter-defibrillator, did not experience additional episodes of TdP during hospitalisation, and was discharged from the hospital on day 13.

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.

Methadone-associated Q-T interval prolongation and torsades de pointes

PURPOSE

The association of methadone with Q-T interval prolongation and torsades de pointes (TdP) is reviewed, and recommendations for preventing Q-T interval prolongation in methadone users are provided.

SUMMARY

Abnormalities in voltage-gated potassium channels have been shown to lead to prolonged action potentials that are expressed as long Q-T intervals, and methadone has been found to interact with the voltage-gated potassium channels of the myocardium. While cardiac arrhythmias in methadone users have been reported for several decades, specific reports of methadone-associated Q-T interval prolongation and TdP did not appear in the literature until the early part of the 21st century. Because not every patient experiences Q-T interval prolongation with methadone, recent research has elucidated risk factors that predispose patients to this adverse effect, including female sex, hypokalemia, high-dose methadone, drug interactions, underlying cardiac conditions, unrecognized congenital long Q-T interval syndrome, and predisposing DNA polymorphisms. Given the high mortality rates seen in untreated illicit opioid users and the clear efficacy of methadone in treating opioid addiction, the risk of using methadone, even in a patient with other risk factors for Q-T interval prolongation, may outweigh the alternative of no pharmacologic treatment. A baseline electrocardiogram (ECG), personal and family history of syncope, and a complete medication history should be obtained before a patient begins treatment with methadone. Given the apparent synergistic effects of parenteral methadone and chlorobutanol, oral methadone should be used whenever possible.

CONCLUSION

Q-T interval prolongation and TdP associated with the use of methadone are potentially fatal adverse effects. A thorough patient history and ECG monitoring are essential for patients treated with this agent, and alterations in treatment options may be necessary.

Ciprofloxacin-induced torsades de pointes in a methadone-dependent patient

ABSTRACT Background Methadone has been associated with QT prolongation and Torsades de pointes. Ciprofloxacin may prolong QT interval and induce Torsades de pointes when other risk factors are present. Case description A case is described in which a patient receiving methadone treatment developed Torsades de pointes following the addition of ciprofloxacin. Conclusion Ciprofloxacin should be used with caution in patients receiving methadone.