A community-based evaluation of sudden death associated with therapeutic levels of methadone

Research gaps on methadone harms and comparative harms: findings from a review of the evidence for an American Pain Society and College on Problems of Drug Dependence clinical practice guideline

Methadone-associated overdose deaths have dramatically increased. In order to inform an evidence-based clinical practice guideline to improve safety of methadone prescribing, the American Pain Society commissioned a systematic review on various aspects related to methadone safety. We searched Ovid MEDLINE, Cochrane Library, and PsycINFO databases through July 2012 to identify studies that addressed 1 or more of 17 Key Questions related to methadone safety; an update search was performed in 2014 for new studies related to methadone-related overdose and risks related to cardiac arrhythmias. A total of 168 studies met inclusion criteria for the review. The purpose of this article is to highlight critical research gaps in the literature related to methadone safety. These include lack of evidence on risk factors associated with methadone-overdose deaths and adverse events, limited evidence to evaluate the comparative mortality of methadone versus other opioids, insufficient evidence to fully understand the harms associated with methadone use during pregnancy, and insufficient evidence to determine effects of risk mitigation strategies such as electrocardiogram monitoring, strategies for managing patients with prolonged QTc intervals on screening, urine drug testing, alternative dosing regimens for initiation and titration of therapy, and timing of follow-up. Therefore, most guideline recommendations are based on weak evidence. More research is needed to guide safe methadone prescribing practices and decrease the adverse events associated with methadone.

PERSPECTIVE

This article summarizes critical research gaps in the literature related to methadone safety, based on a systematic review commissioned by the American Pain Society. Critical research gaps were identified in a number of areas, highlighting the need for additional research to guide safer prescribing and risk mitigation strategies.

Methadone overdose and cardiac arrhythmia potential: findings from a review of the evidence for an American Pain Society and College on Problems of Drug Dependence clinical practice guideline

The number of deaths associated with methadone use increased dramatically in parallel with marked increases in its use, particularly for treatment of chronic pain. To develop a clinical guideline on methadone prescribing to reduce potential harms, the American Pain Society commissioned a review of various aspects related to methadone safety. This article summarizes evidence related to unintentional overdose due to methadone and harms related to cardiac arrhythmia potential. We searched Ovid MEDLINE, the Cochrane Library, and PsycINFO databases through January 2014 for studies assessing harms associated with methadone use; we judged 70 studies to be relevant and to meet inclusion criteria. The majority of studies on overdose and cardiac arrhythmia risk are observational and provide weak evidence on which to base clinical guidelines. In patients prescribed methadone for treatment of opioid dependence, data suggest that mortality benefits related to reduction in illicit drug use outweigh harms. Despite epidemiologic data showing marked increases in the numbers of methadone-related deaths that have been primarily attributed to increased use of methadone for chronic pain, evidence on methadone and mortality risk in this population has been somewhat contradictory. There is some evidence that recent initiation of methadone, psychiatric admissions, and concomitant use of benzodiazepines are associated with a higher risk for overdose. Evidence on cardiac risks is primarily limited to case reports of torsades de pointes, primarily in patients on high doses of methadone, and to studies showing an association between methadone use and prolongation of QTc intervals. Research is needed to understand the effectiveness of dosing methods, electrocardiogram monitoring, and other risk mitigation strategies in patients prescribed methadone.

PERSPECTIVE

This systematic review synthesizes the evidence related to methadone use and risk for overdose and cardiac arrhythmia. Findings regarding the association between methadone use and QTc interval prolongation and risk factors for methadone-associated overdose suggest potential targets for risk mitigation strategies, though research is needed to determine the effectiveness of such strategies at reducing adverse outcomes.

The opioid methadone induces a local anaesthetic-like inhibition of the cardiac Na⁺ channel, Na(v)1.5

BACKGROUND AND PURPOSE

Treatment with methadone is associated with severe cardiac arrhythmias, a side effect that seems to result from an inhibition of cardiac hERG K⁺ channels. However, several other opioids are inhibitors of voltage-gated Na⁺ channels. Considering the common assumption that an inhibition of the cardiac Na⁺ channel Na(v)1.5, is the primary mechanism for local anaesthetic (LA)-induced cardiotoxicity, we hypothesized that methadone has LA-like properties leading to a modulation of Na(v)1.5 channels.

EXPERIMENTAL APPROACH

The whole-cell patch clamp technique was applied to investigate the effects of methadone on wild-type and mutant human Na(v)1.5 channels expressed in HEK293 cells. A homology model of human Na(v)1.5 channels was used to perform automated ligand-docking studies.

KEY RESULTS

Methadone inhibited Na(v)1.5 channels in a state-dependent manner, that is, tonic block was stronger with inactivated channels than with resting channels and a use-dependent block at 10 Hz. Methadone induced a concentration-dependent shift of the voltage dependency of both fast and slow inactivation towards more hyperpolarized potentials, and impaired recovery from fast and slow inactivation. The LA-insensitive mutants N406K and F1760A exhibited reduced tonic and use-dependent block by methadone, and docking predictions positioned methadone in a cavity that was delimited by the residue F1760. Dextromethadone and levomethadone induced discrete stereo-selective effects on Na(v)1.5 channels.

CONCLUSIONS AND IMPLICATIONS

Methadone interacted with the LA-binding site to inhibit Na(v)1.5 channels. Our data suggest that these channels are a hitherto unrecognized molecular component contributing to cardiac arrhythmias induced by methadone.

Chronic pain treatment with opioid analgesics: benefits versus harms of long-term therapy

Chronic non-cancer pain (CNCP) is a disabling chronic condition with a high prevalence rate around the world. Opioids are routinely prescribed for treatment of chronic pain (CP). In the past two decades there has been a massive increase in the number of opioid prescriptions, prescribed daily opioid doses and overall opioid availability. Many more patients with CNCP receive high doses of long-acting opioids on a long-term basis. Yet CP and related disability rates remain high, and majority of the patients with CNCP are dissatisfied with their treatments. Intersecting with the upward trajectory in opioid use are the increasing trends in opioid related adverse effects, especially prescription drug abuse, addiction and overdose deaths. This complex situation raises questions on the relevance of opioid therapy in the treatment of CNCP. This article reviews current evidence on opioid effectiveness, the benefits and harms of long-term therapy in CNCP.

Use of Mindfulness Meditation in the Management of Chronic Pain

Background. Chronic pain is a major health condition that has significant financial and lifestyle implications. Due to the complex etiologies of pain, it is difficult to find treatment modalities that would be universally applicable to the general population presenting for care. Mindfulness meditation is a complimentary treatment modality that has some preliminary, inconclusive evidence in support of its benefit on patients with chronic pain. Objectives. The purpose of this article is to systematically review the current literature for randomized controlled trials that assess the outcomes of mindfulness as an intervention for individuals with chronic pain. Methods. An electronic database search was performed for studies investigating the efficacy of mindfulness in treatment for chronic pain. The studies included were randomized controlled trials, published in English, from a peer-reviewed journal that identified mindfulness as the primary treatment focus for chronic pain in at least one group, and included participants with at least a 12-week history of symptoms. Results. The database search revealed 283 articles, of which 6 met the inclusion criteria. Conclusion. Mindfulness meditation appears to have minimal or statistically insignificant effects on chronic pain according to the current data. However, the effects of mindfulness on mental health scores are significant and may be an area for future trials to target. Well-conducted research is necessary before the effects of mindfulness on chronic pain can be definitively determined.

Methadone-related deaths - epidemiological, pathohistological, and toxicological traits in 10-year retrospective study in Vojvodina, Serbia

The number of methadone-related deaths (MRDs) during a 10-year period (2002-2011) in the region of Vojvodina, Serbia, was increased. The cases were evaluated according to epidemiological parameters, pathohistological findings, and toxicological screening. The majority of victims were men, aged from 20 to 38. Pathohistologically, the signs of acute focal myocardial damage were present in the heart of victims with drug abuse history shorter than 2 years, while both signs of recent and chronic focal myocardial damage were developed among victims with longer drug abuse history (2-5 years). In postmortem blood samples of 54.84% of victims, methadone was detected in combination with diazepam, both in therapeutic range. Alcohol was absent in most cases. Other detected drugs were antipsychotics and antidepressants in therapeutic concentrations. These findings raise the attention to the concomitant use of methadone and benzodiazepines with the need for further studies to clarify the mechanism of death in such cases.

Relationship Between Seizure Episode and Sudden Cardiac Arrest in Patients With Epilepsy

Background—

Among patients with epilepsy, sudden cardiac arrest (SCA) is a major cause of death. It is commonly thought that SCA in epilepsy occurs after a seizure, though the strength of evidence supporting this is limited. We sought to evaluate the relationship between seizures and SCA in patients with epilepsy.

Methods and Results—

From the ongoing Oregon Sudden Unexpected Death Study, cases of SCA identified using prospective, multisource ascertainment (Portland metropolitan area, Oregon; population ≈1 million; February 1, 2002, to March 1, 2012) were evaluated for history of epilepsy. In the subset with witnessed SCA, clinical presentations were analyzed for evidence of seizure activity immediately before the event as well as lifetime clinical history, including nature of seizures before SCA. Only 34% of patients with history of epilepsy and a witnessed arrest had evidence of seizure activity before the arrest. Rates of survival to hospital discharge after attempted resuscitation were 2.7% in patients with history of epilepsy versus 11.9% for patients without epilepsy ( P =0.014). Patients with epilepsy had a significantly lower rate of presentation with ventricular tachycardia/ventricular fibrillation as opposed to pulseless electrical activity/asystole (epilepsy, 26%; no epilepsy, 44%; P =0.002), despite nearly identical response times.

Conclusions—

In the majority (66%) of epilepsy patients, there was no relationship between seizure and SCA, implying that SCA in epilepsy patients often may not involve seizure as a trigger. The significantly worse rate of survival from SCA in epilepsy patients warrants urgent investigation.

Effectiveness of naltrexone in the prevention of delayed respiratory arrest in opioid-naive methadone-intoxicated patients

Acute methadone toxicity is a major public health concern in Iran. Methadone-intoxicated patients are in a great risk of recurrent or delayed respiratory arrest despite the prescription of initial doses of naloxone. This study aimed to evaluate the effectiveness of oral naltrexone in the management of acute methadone overdose in opioid-naive patients and check if it could be a substitute of continuous infusion of naloxone in maintaining adequate ventilation. In a randomized, double-blind, placebo-controlled study, a total of 54 opioid-naive patients with acute methadone toxicity were enrolled. The patients received either oral naltrexone or placebo capsules after awakening by naloxone. All patients underwent close monitoring of respiration. Frequency of respiratory depression or arrest, need for another dose of naloxone, duration of hospital stay, and adverse outcomes compared between the two groups. The incidence of respiratory depression was significantly less in those who had received naltrexone. Our results show that single oral dose of naltrexone is quite efficient in the prevention of recurrent or delayed respiratory arrest in opioid-naive methadone-intoxicated patients. It can shorten the duration of hospitalization and, as a consequence, decreased the risk of complications. Further studies are warranted before the generalization of this approach to other patient populations.

Risk factors for fatal outcome in patients with opioid dependence treated with methadone in a family medicine setting in Croatia

AIM

To determine the risk factors for fatal outcome in patients with opioid dependence treated with methadone at the primary care level.

METHODS

A group of 287 patients with opioid dependence was monitored prospectively from 1995 to 2007. At the beginning of the study, we collected the data on patient baseline characteristics, treatment characteristics, and living environment. At the annual check-up, we collected the data on daily methadone dose, method of methadone therapy administration, and family physician's assessment of the patient's drug use status.

RESULTS

Out of 287 patients, 8% died. Logistic regression analysis showed that the predictors of fatal outcome were continuation of drug use during previous therapeutic attempts (odds ratio [OR], 19.402; 95% confidence interval [CI], 1.659-226.873), maintenance therapy as the planned treatment modality (OR, 3.738; 95% CI, 1.045-13.370), living in an unstable relationship (OR, 9.275; 95% CI, 2.207-38.984), and loss of continuity of care (OR, 12.643; 95% CI, 3.001-53.253).

CONCLUSION

The patients presenting these risk factors require special attention. It is important for family physicians to insist on compliance with the treatment protocol and intervene when they lose contact with the patient to prevent the fatal outcome.

Methadone, QTc interval prolongation and torsade de pointes: Case reports offer the best understanding of this problem

We reviewed the literature and found 31 adult cases and 1 newborn case of methadone-associated QTc interval prolongation and/or torsade de pointes (TdP). Parametric statistics may not be useful in studying this issue because methadone-associated TdP is a very rare event and, hence, "an extreme outlier" consistent with scalable randomness. We may have to rely upon narrative medicine in the form of case reports with all its limitations and hazards to provide our best understanding. We report risk factors for methadone-associated QTc interval prolongation and TdP based on review of published case reports. We believe both drug manufacturers and the FDA would better serve our patients and inform clinicians if they more readily reported drug-induced outliers such as methadone-associated TdP using a case report format.

QTc interval screening for cardiac risk in methadone treatment of opioid dependence

BACKGROUND

Methadone represents today the gold standard of efficacy for the pharmacological treatment of opioid dependence. Methadone, like many other medications, has been implicated in the prolongation of the rate-corrected QT (QTc) interval of the electrocardiogram (ECG), which is considered a marker for arrhythmias such as torsade de pointes (TdP). Indications on the association between methadone, even at therapeutic dosages, and TdP or sudden cardiac death have been reported. On these bases, consensus and recommendations involving QTc screening of patients receiving methadone treatment have been developed to identify patients with QTc above the thresholds considered at risk for cardiac arrhythmias, and they provide these individuals with alternative treatment (reduction of methadone dosage; provision of alternative opioid agonist treatment; treatment of associated risk factors).

OBJECTIVES

To evaluate the efficacy and acceptability of QTc screening for preventing cardiac-related morbidity and mortality in methadone-treated opioid dependents.

SEARCH METHODS

We searched MEDLINE, EMBASE, CINAHL (to April 2013), the Cochrane Central Register of Controlled Trials (CENTRAL), The Cochrane Library Cochrane Drug and Alcohol Review Group Specialised Register (Issue 3, 2013), main electronic sources of ongoing trials, specific trial databases and reference lists of all relevant papers.

SELECTION CRITERIA

Randomised controlled trials (RCTs), controlled clinical trials (CCTs) and non-randomised studies (cohort studies, controlled before and after studies, interrupted time series studies, case control studies) examining the efficacy of QTc screening for the prevention of methadone-related mortality and morbidity in opioid addicts.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened and extracted data from studies.

MAIN RESULTS

The search strategy led to the identification of 872 records. Upon full-text assessment, no study was found to meet the quality criteria used for this review.

AUTHORS' CONCLUSIONS

It is not possible to draw any conclusions about the effectiveness of QTc screening strategies for preventing cardiac morbidity/mortality in methadone-treated opioid addicts. Research efforts should focus on strengthening the evidence about the effectiveness of widespread implementation of such strategies and clarifying the associated benefits and harms.

Trends in reporting methadone-associated cardiac arrhythmia, 1997-2011: an analysis of registry data

BACKGROUND

Long-acting opioids are a leading cause of accidental death in the United States, and methadone is associated with greater mortality rates. Whether this increase is related to the proarrhythmic properties of methadone is unclear.

OBJECTIVE

To describe methadone-associated arrhythmia events reported in the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS).

DESIGN

Description of national adverse event registry data before and after publication of a 2002 report describing an association between methadone and arrhythmia.

SETTING

FAERS, November 1997 and June 2011.

PATIENTS

Adults with QTc prolongation or torsade de pointes and ventricular arrhythmia or cardiac arrest.

MEASUREMENTS

FAERS reports before and after the 2002 report.

RESULTS

1646 cases of ventricular arrhythmia or cardiac arrest and 379 cases of QTc prolongation or torsade de pointes were associated with methadone. Monthly reports of QTc prolongation or torsade de pointes increased from a mean of 0.3 (95% CI, 0.1 to 0.5) before the 2002 publication to a mean of 3.5 (CI, 2.5 to 4.8) after it. After 2000, methadone was the second-most common primary suspect in cases of QTc prolongation or torsade de pointes after dofetilide (a known proarrhythmic drug) and was associated with disproportionate reporting similar to that of antiarrhythmic agents known to promote torsade de pointes. Antiretroviral drugs for HIV were the most common coadministered drugs.

LIMITATION

Reports to FAERs are voluntary and selective, and incidence rates cannot be determined from spontaneously reported data.

CONCLUSION

Since 2002, reports to FAERS of methadone-associated arrhythmia have increased substantially and are disproportionately represented relative to other events with the drug. Coadministration of methadone with antiretrovirals in patients with HIV may pose particular risk.

PRIMARY FUNDING SOURCE

Colorado Clinical and Translational Sciences Institute, National Institutes of Health, and Agency for Healthcare Research and Quality.

Opioid and chronic non-cancer pain

Although, opioids are advocated in various guidelines their use for chronic non-cancer pain is controversial because evidence of long term benefit is weak. The potential for serious adverse effects and local regulations promote caution in both the prescribers and users. However, opioids have a place in the management of chronic non-cancer pain in carefully selected patients with regular monitoring and as a part of the multimodal therapy. It is important for the treating physician to be up-to-date with this form of therapy, in order to have the necessary confidence to prescribe opioids and manage adverse effects. The common adverse effects should be treated promptly to improve patient compliance. We believe that opioid therapy in low doses is beneficial to some patients. It should not be denied but carefully considered on case by case basis.

Methadone-related deaths in Montpellier and Region, from 2000 to 2010

PURPOSE

The objectives of this analysis were to assess the role of methadone and related substances in death occurring, discussing methadone blood concentrations and the contribution of the autopsy to the accountability of methadone in the death process.

METHOD

We retrospectively analyzed all forensic cases positive for methadone from January 2000 to December 2010, in Montpellier and the region served by our laboratory.

RESULTS

During the study period, 64 cases of deaths (11 women, 53 men) with methadone detection were recorded. A progressive increase between 2001 (2 cases) and 2010 (8 cases) was observed. The median age was 33 years old. An autopsy was available in 56.3% of cases. The most frequent finding at the autopsy was non-specific asphyxia death signs (67.6%). Tolerance to opioids was documented in 21 cases. The methadone blood concentrations ranged from 1 to 2 800 ng/mL (59 cases, median value 330 ng/mL). Most of the cases (88%) were polydrug intoxications. The most commonly associated drugs were benzodiazepines (61%), cannabinoids (28%), opioids (19%) and cocaine (12.5%).

CONCLUSION

During a 11-year period, toxicological analyses related to 1991 death cases were performed at the Toxicology Laboratory of Montpellier University Hospital. Of these patients, 64 deaths were possibly related to methadone. Several relevant elements (biological analysis and autopsy) were used to attribute the deaths to the sole methadone (12 cases) or to methadone and associated substances (8 cases).

Methadone for chronic non-cancer pain in adults

BACKGROUND

Methadone belongs to a class of analgesics known as opioids, that are considered the cornerstone of therapy for moderate-to-severe pain due to life-threatening illnesses; however, their use in chronic non-cancer pain (CNCP) is controversial. Methadone has many characteristics that differentiate it from other opioids, which suggests that it may have a different efficacy and safety profile.

OBJECTIVES

To assess the analgesic effectiveness and safety of methadone in the treatment of CNCP.

SEARCH METHODS

We identified both randomized controlled trials (RCTs) and non-randomized studies of methadone use in chronic pain by searching the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library 2011, issue 11, MEDLINE (1950 to November 2011), and EMBASE (1980 to November 2011), together with reference lists of retrieved papers and reviews.

SELECTION CRITERIA

We included RCTs with pain assessment as either the primary or secondary outcome. Quasi-randomized studies, cohorts and case-control trials were also considered for inclusion because we suspected that the beneficial and harmful effects of methadone in CNCP may not be adequately addressed in RCTs.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted efficacy and adverse event data and assessed risk of bias.

MAIN RESULTS

We included two RCTs and one non-randomized study, involving a total of 181 participants. Both RCTs were cross-over studies, one involving 19 participants with diverse neuropathic pain syndromes, the other involving 76 participants with postherpetic neuralgia. Study phases were 20 days and approximately eight weeks, respectively. The non-randomized study retrospectively evaluated 86 outpatients over an average of 8.8 ± 6.3 months.One RCT reported average pain intensity and pain relief, and found statistically significant improvements versus placebo for both outcomes, with 10 mg and 20 mg daily doses of methadone. The second RCT reported differences in pain reduction between methadone and morphine and found morphine to be statistically superior. The non-randomized study found that in patients initially prescribed methadone it was effective in fewer participants than in those initially prescribed other long-acting opioids (28% versus 42%, 33% and 50% for morphine, oxycodone and transdermal fentanyl, respectively).One RCT compared incidences for several individual adverse events, but found a difference between methadone and placebo for only one event, dizziness (P = 0.041).

AUTHORS' CONCLUSIONS

The three studies provide very limited evidence of the efficacy of methadone for CNCP, and there were too few data for pooled analysis of efficacy or harm, or to have confidence in the results of the individual studies. No conclusions can be made regarding differences in efficacy or safety between methadone and placebo, other opioids, or other treatments.

Informed consent in opioid therapy: a potential obligation and opportunity

Most patients receiving opioids for the spectrum of pain disorders tolerate opioids well without major complications. However, a subset of this population encounters significant difficulties with opioid therapy (OT). These problems include protracted adverse effects, as well as misuse, abuse, and addiction, which can result in significant morbidity and mortality and make informed consent an important consideration. Opioid treatment agreements (OTAs), which may include documentation of informed consent, have been used to promote the safe use of opioids for pain. There is a debate regarding the effectiveness of OTAs in reducing the risk of opioid misuse; however, most practitioners recognize that OTAs provide an opportunity to discuss the potential risks and benefits of OT and establish mutually agreed-on treatment goals, a clear plan of treatment, and circumstances for continuation and discontinuation of opioids. Informed consent is an important component of an OTA but not often the focus of consideration in discussions of OTAs. This article examines the principles, process, and content of informed consent for OT of pain in the context of OTAs.

The clinical significance of QT interval prolongation in anesthesia and pain management: what you should and should not worry about

The most feared drug-induced complication is fatal cardiac arrest. Torsades de pointes (TdP) is a polymorphic ventricular tachycardia occurring in the setting of a QT interval prolongation and is the most frequent type of drug-induced pro-arrhythmia. The most common mechanism of QT prolongation and TdP is blockade of the rapid component of the delayed rectifier repolarizing potassium conductance IKr. Anesthesiologists have extensive experience with QT prolonging drugs, but there are relatively few reports of TdP occurring in the perioperative setting. Nevertheless, regulatory concern regarding the drug droperidol resulted in a significant reduction in its use. Concern regarding two other agents that potently block IKr, i.e., sevoflurane and methadone, has grown, and practitioners are worried that these valuable agents may meet the same fate. In this review, the data regarding the TdP risk of droperidol, sevoflurane, and methadone are compared with particular emphasis on the different settings in which they are employed. While the three drugs are potent IKr inhibitors, little evidence exists to suggest that droperidol or sevoflurane are associated with significant proarrhythmia in the perioperative setting. Due to factors such as inhibition of the parasympathetic nervous system, prevention of hypoxia and hypercarbia, and attention to serum electrolytes, TdP is a very rare occurrence in the perioperative environment. Methadone, however, is typically given to outpatients, over long periods, and in combination with agents that inhibit its metabolism or are QT prolonging in their own right. Thus, pre- and post-drug electrocardiograms may be appropriate when prescribing methadone for outpatients, while the much lower risk for TdP (and the difficulties inherent in QT measurement in the perioperative period) render this approach unfruitful and worthy of reevaluation.

Cardiac autonomic modulation during methadone therapy among heroin users: a pilot study

BACKGROUND

Methadone therapy benefits heroin users in both the medical and psychosocial dimensions. However, both heroin and methadone have cardiac toxicity. Only limited information is available describing the changes in cardiac autonomic function of heroin users and effects of methadone therapy. We conduct the current study to explore the cardiac vagal function in heroin users as well as the impact of lapse and methadone therapy.

METHODS

80 heroin users from a methadone therapy clinic were distributed into 31 compliant and 49 incompliant patients according to whether they lapsed into heroin use within 10 days. 40 healthy control subjects were recruited from the community. Participants underwent electrocardiographic recordings and the heroin users were further investigated before and after methadone therapy. Spectral analysis of heart rate variability (HRV) was computed for cardiac parasympathetic modulation (high-frequency power, HF) and cardiac sympathetic modulation (normalized low-frequency power, LF%).

RESULTS

The baseline HRV parameters found lower HF values for heroin users and lower RR interval values for patients with a recent lapse compared with the healthy control subjects. After 1h of methadone administration, heroin users who had lapsed showed a significant increase in HF but the heroin users who had not lapsed did not.

CONCLUSION

Our findings suggest that heroin users show decreased cardiac vagal activity and that methadone therapy immediately facilitates vagal regulation in patients with a recent lapse. The differential patterns of autonomic alteration under methadone between those with and without lapse might offer an objective measure of lapse.

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.

Methadone toxicity due to smoking cessation--a case report on the drug-drug interaction involving cytochrome P450 isoenzyme 1A2

OBJECTIVE

To report the potential clinically significant pharmacokinetic interaction that may result from smoking cessation in patients on methadone maintenance therapy.

CASE SUMMARY

A 46-year-old white man was admitted to the step-down intensive care unit with decreased respirations and altered mental status related to methadone toxicity. The patient had been on a stable dose of methadone for chronic back pain, and he reported a 1 pack per day, 33-year history of cigarette smoking. After methadone was held for 3 days, his mental status improved. It was later revealed that he had initiated smoking cessation. He was discharged home on a reduced dose of methadone with no further complications.

DISCUSSION

While the potential for toxicity exists for patients who are maintained on methadone and decrease the number of cigarettes they smoke, to our knowledge, there is no recent peer-reviewed literature on this interaction. Methadone is a synthetic opioid primarily metabolized by CYP3A4 and, to a lesser degree, by other isoenzymes, including CYP1A2. Polycyclic aromatic hydrocarbons found in tobacco smoke are known CYP1A2 inducers. Decreased intake of cigarette smoke can lead to a reduction in methadone metabolism, resulting in higher serum concentrations. Our case is an example of methadone toxicity secondary to smoking cessation in a patient on methadone maintenance therapy. An objective causality assessment based on the Horn Drug Interaction Probability Scale revealed the interaction to be probable.

CONCLUSIONS

Patients on methadone should be monitored for signs of methadone toxicity upon the start of smoking cessation, and the dose of methadone should be adjusted accordingly. Additional information and reports cautioning clinicians and patients about this potential interaction would be beneficial.

Comparative mortality among Department of Veterans Affairs patients prescribed methadone or long-acting morphine for chronic pain

Data on comparative safety of opioid analgesics are limited, but some reports suggest disproportionate mortality risk associated with methadone. Our objective was to compare mortality rates among patients who received prescribed methadone or long-acting morphine for pain. This is a retrospective observational cohort drawn from Department of Veterans Affairs (VA) health care databases, January 1, 2000, to December 31, 2007. We included 28,554 patients who received methadone and 79,938 who received long-acting morphine from VA pharmacies. Compared with those who received long-acting morphine, patients who received methadone were younger, less likely to have some medical comorbidities, and more likely to have psychiatric and substance use disorders. Patients were stratified into quintiles according to propensity score; the probability of receiving methadone was conditional on demographic, clinical, and VA service area variables. Overall propensity-adjusted mortality was lower for methadone than for morphine. Hazard ratios varied across propensity score quintiles; the magnitude of the between-drug difference in mortality decreased as the propensity to receive methadone increased. Mortality was significantly lower for methadone in all but the last quintile, in which there was no between-drug difference in mortality (hazard ratio=0.92, 95% confidence interval=0.74, 1.16). Multiple sensitivity analyses found either no difference in mortality between methadone and long-acting morphine or lower mortality rates among patients who received methadone. In summary, we found no evidence of excess all-cause mortality among VA patients who received methadone compared with those who received long-acting morphine. Randomized trials and prospective observational research are needed to better understand the relative safety of long-acting opioids.

Cardiovascular-associated disease in an addicted population: an observation study

BACKGROUND

Illicit drugs such as cocaine, and methadone can induce acquired long QT syndrome.

OBJECTIVE

The aim of this study was to evaluate the prevalence of cardiovascular disease and to assess the risk of torsades de pointes in substance abuse patients either with methadone or buprenorphine maintenance therapy, or without any specific therapy for opiate addiction.

METHODS

From November 2008 to December 2009, 190 patients (153 men, mean age 38.2 years, 22-56 years) with a substance use disorder according to DSM IV TR criteria were included in the study. All patients underwent blood tests, serial electrocardiogram (ECG) and, when necessary, additional testing, including echocardiogram, exercise test and Holter monitoring. Age and sex-matched healthy controls were also evaluated and compared with the cases.

RESULTS

One hundred and twenty-five patients (65.7%) had associated diseases. The prevalence of coronary artery disease and hypertension was, respectively, 2.1 and 5.2% in the addicted population. The percentage of abnormal ECGs was 34.2% in the addicted population and 4.7% in the nonaddicted population (P < 0.001). Twenty-five addicted patients had a QT interval prolongation (10 patients ≥ 480 ms). There were no sudden deaths or major cardiac events during the observation period.

CONCLUSIONS

Our results indicate that the QT interval prolongation is not a negative prognostic marker in the addicted population, even with associated diseases. ECG should be performed when other drugs potentially prolonging QT interval are associated. Substance abuse patients should be followed by multidisciplinary teams, and blood tests and ECGs should be performed regularly.

Increased cardiac risk in concomitant methadone and diazepam treatment: pharmacodynamic interactions in cardiac ion channels

Methadone, a synthetic opioid for treatment of chronic pain and withdrawal from opioid dependence, has been linked to QT prolongation, potentially fatal torsades de pointes, and sudden cardiac death. Concomitant use of diazepam or other benzodiazepines in methadone maintenance treatment can increase the risk of sudden death. Therefore, we determined the effects of methadone and diazepam singly and in combination on cardiac action potentials (APs) and on the major ion channels responsible for cardiac repolarization. Using patch clamp recording in human stem cell-derived cardiomyocytes and stably transfected mammalian cells, we found that methadone produced concentration-dependent AP prolongation and ion channel block at low micromolar concentrations: hERG (IC50 = 1.7 μM), hNav1.5 (11.2 μM tonic block; 5.5 μM phasic block), and hCav1.2 (26.7 μM tonic block; 7.7 μM phasic block). Methadone was less potent in hKv4.3/hKChIP2.2 (IC50 = 39.0 μM) and hKvLQT1/hminK (53.3 μM). In contrast, diazepam blocked channels only at much higher concentrations and had no effect on AP duration at 1 μM. However, coadministration of 1-μM diazepam with methadone caused a statistically significant increase in AP duration and a 4-fold attenuation of hNav1.5 block (IC50 values were 44.2 μM and 26.6 μM, respectively, for tonic and phasic block), with no significant effect on methadone-induced block of hERG, hCav1.2, hKv4.3/hKChIP2.2, and hKvLQT1/hminK channels. Thus, although diazepam alone does not prolong the QT interval, the relief of methadone-induced Na channel block may leave hERG K channel block uncompensated, thereby increasing cardiac risk.

Pharmacokinetic drug interactions and adverse consequences between psychotropic medications and pharmacotherapy for the treatment of opioid dependence

BACKGROUND

Psychiatric comorbidities among opioid-dependent patients are common. Many medications used to treat both conditions are metabolized through complimentary cytochrome P450 isoenzymes. When medication-assisted treatment for opioid dependence is concurrently used with psychotropic medications, problematic pharmacokinetic drug interactions may occur.

METHODS

We reviewed relevant English language articles identified through the MedLine, Scopus, and Embase databases from 1950 to December 2009 using the specific generic names of medications and keywords such as pharmacokinetics and drug interactions with buprenorphine, methadone, and naltrexone. Selected references from these articles were reviewed. Additionally, a review was conducted of abstracts and conference proceedings from national and international meetings from 1990 to 2009. A total of 60 studies were identified and reviewed.

RESULTS

Clinical case series and carefully controlled pharmacokinetic interaction studies have been conducted between methadone, buprenorphine, or naltrexone and some psychoactive medications. Important pharmacokinetic drug interactions have been demonstrated within each class of medications affecting either methadone and buprenorphine or psychoactive drugs. Few studies, however, have been conducted with naltrexone.

CONCLUSIONS

Several interactions between methadone, buprenorphine, or naltrexone and psychoactive medications are described and may have important clinical consequences. To optimize care, clinicians must be alerted to these interactions.

An unusual case of accidental poisoning: fatal methadone inhalation

In this report, the authors present a case of unusual, accidental methadone intoxication in a 40-year-old man, who had inhaled methadone powder. The drug dealer was a pharmacy technician; methadone had been stolen from a pharmacy and sold as cocaine. After having inhaled methadone powder, he suffered cardiopulmonary arrest. He was admitted to hospital where he died after 24 h of intensive care. The autopsy revealed congestion of internal organs and cerebral and pulmonary edema. Microscopically, the heart showed no changes. The toxicological analyses performed on blood and urine taken at the hospital revealed methadone, cannabinoids, and ethanol. The blood methadone concentration was 290 μg/L. The urine methadone concentration was 160 μg/L. Midazolam and lidocaine, which were administered to the patient at the hospital, were also detected in the blood. The cause of death was determined to be methadone intoxication. The literature has been reviewed and discussed. To date, and to our knowledge, only very few cases of accidental death resulting from methadone inhalation have been described up to the case presented herein.

Inhibitory action of methadone and its metabolites on erg-mediated K+ current in GH₃ pituitary tumor cells

Methadone (Mtd) is a widely used opioid drug associated with the side effect of hyperprolactinemia. The mechanism of how Mtd induces prolactin secretion remains unclear. The effects of Mtd and its two main metabolites (EDDP: (±)-2-ethyl-1,5-dimethyl-3,3-diphenylpyrrolinium percholarate and EMDP: 2-ethyl-5-methyl-3,3-dipnehyl-1-pyrroline) on ion currents were investigated in GH₃ pituitary tumor cells. Hyperpolarization-elicited K+ currents in GH₃ cells bathed in a high-K(+), Ca(2+)-free solution were studied to evaluate the effects of Mtd and other related compounds on the ether-à-go-go-related-gene (erg) K(+) current (I(K(erg))). Mtd suppressed the amplitude of I(K(erg)) in a concentration-dependent manner with an IC(50) value of 10.4 μM. With the aid of a minimal binding scheme, the inhibitory action of Mtd on I(K(erg)) was estimated with a dissociation constant of 8.2 μM. Mtd tended to increase the rate of I(K(erg)) deactivation in a voltage-dependent fashion. EDDP (10 μM) had no effect on I(K(erg)), while EMDP (10μM) slightly suppressed it. In GH₃ cells incubated with naloxone (30 μM), the Mtd-induced inhibition of I(K(erg)) remained unaltered. Under cell-attached voltage-clamp recordings, Mtd increased the frequency of spontaneous action currents with no change in current amplitude. Similarly, Mtd can suppress I(K(erg)) in differentiated NG108-15 cells; dynorphin A(1-13) did not reverse Mtd-induced inhibition of I(K(erg)). This study shows that Mtd has a depressant effect on I(K(erg)), and suggests its ability to affect membrane excitability and prolactin secretion. The cyclization of Mtd, in which EDDP and EMDP are formed, tends to be critical in removal of the Mtd binding to erg K+ channel.

Early identification of risk factors for sudden cardiac death

Sudden cardiac death (SCD) is a global health issue. The unexpected nature of this devastating condition compounds the urgency of discovering methods for early detection of risk, which will lead to more effective prevention. However, the complex and dynamic nature of SCD continues to present a considerable challenge for the early identification of risk factors. Measurement of the left ventricular ejection fraction (LVEF) is currently the only major risk factor used for stratification in clinical practice. Severely decreased LVEF is likely to manifest late in the natural history of SCD, however, and may only affect a small subgroup of patients who will suffer SCD. A growing body of literature describes novel risk markers and predictors of SCD, such as high-risk phenotypes, genetic variants and biomarkers. This Review will discuss the potential utility of these markers as early identifiers of risk, and suggests a framework for the conduct of future studies for the discovery, validation, and deployment of novel SCD risk factors.

Methadone deaths: risk factors in pain and addicted populations

Methadone is highly effective in treating opioid dependence, and it is also used as an analgesic for second-line management of chronic pain. However, recent increases in methadone-related deaths have instigated controversy about the use of this medication. In this paper, we evaluate risk factors for methadone mortality in opioid dependent and pain populations and present guidelines for initiating methadone treatment in these two populations to minimize the risk of death. Early research with methadone-maintained patients revealed that methadone fatalities occur primarily due to respiratory arrest during methadone induction and in the context of polysubstance use. Recent reports of methadone deaths emphasize chronic pain populations, methadone-related QTc prolongation, and the possibility of inducing Torsade de pointes (TdP), a potentially fatal ventricular arrhythmia. Retrospective analyses of these deaths show that patients who develop TdP often present with multiple risk factors, including high methadone doses, use of other medications that cause QTc prolongation, and electrolyte abnormalities. To minimize fatalities, guidelines are presented for initiating methadone in opioid treatment and pain populations that consider the drug's pharmacology along with behavioral, medical and psychiatric risk factors.

Trends in methadone-related deaths in Zurich

Methadone has a long and successful history in the treatment of opioid addiction. In recent years, it has become popular again--as potent and inexpensive analgesic in patients with chronic pain. Since methadone has been used fatalities have been reported. In our study all methadone-associated deaths in Zurich from 1998 to 2007 were analysed. Most of the 146 detected deaths of the past 10 years occurred during substitution programmes or illicit intake of methadone while only three of them could be attributed to methadone used as an analgesic. Noticeable in our study was the high percentage of cases of combined drug intoxication (76%). The most frequent co-intoxicants were alcohol and cocaine. Mortalities attributed to methadone intoxication alone were a rare finding and could only be detected in five cases of deceased who had received methadone maintenance treatment. The aim of our study is to assess the trends in the number and nature of methadone-related fatalities in Zurich during the last 19 years. For this purpose a previous study from Zurich (1989-1997) was included, whereby a very long observation period and large number of cases resulted.

Ventricular arrhythmias in patients treated with methadone for opioid dependence

PURPOSE

Over the last decade, there has been a significant rise in reported cases of methadone induced QT prolongation (QTP) and Torsades de Pointes (TdP) in patients treated for opioid dependence. Optimal management of these patients is challenging.

METHODS

We report a case series of 12 consecutive patients admitted to our institution with methadone-induced QTP and ventricular arrhythmias.

RESULTS

All patients survived the presenting arrhythmia. Successful transition to buprenorphine was accomplished in three patients. QT interval normalized and none of these patients had recurrent arrhythmias. Methadone dose was reduced in five patients with improvement of QT interval and resolution of arrhythmia. Four patients, including two with ICDs, refused or did not tolerate a reduction in their methadone dose.

CONCLUSION

Ventricular arrhythmias in patients on methadone are an uncommon but important problem. Buprenorphine, a partial micro-opiate-receptor agonist and a kappa-opiate-receptor antagonist does not cause QTP or TdP. Buprenorphine is a useful and effective alternative to methadone in a select group of patients, including those with documented ventricular arrhythmias on methadone. Pacemakers or defibrillators should be reserved for patients who have failed buprenorphine or a reduced methadone dose.

Drink, drugs, and the QT interval

The effects of several prescription and illicitly-used drugs on electrocardiographic repolarization are well documented, most frequently manifested as prolongation of the corrected QT (QTc) interval. The combination of multiple repolarization-modulating drugs taken in high dosage can occasionally lead to extreme abnormalities of the QTc interval and ST-segment on the surface ECG, which can lead to the erroneous diagnosis of underlying myocardial ischemia and inappropriate treatment. We report on one such case in which the acute management of a syncopal patient was detrimentally influenced by misinterpretation of a very unusual ECG.

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.