Retrospective analysis of low-dose methadone and QTc prolongation in chronic pain patients

Pain Management Considerations in Patients with Opioid Use Disorder Requiring Critical Care

The opioid epidemic has resulted in increased opioid-related critical care admissions, presenting challenges in acute pain management. Limited guidance exists in the management of critically ill patients with opioid use disorder (OUD). This narrative review provides the intensive care unit (ICU) clinician with guidance and treatment options, including non-opioid analgesia, for patients receiving medications for opioid use disorder (MOUD) and for patients actively misusing opioids. Verification and continuation of the patient's outpatient MOUD regimen, specifically buprenorphine and methadone formulations, assessment of pain and opioid withdrawal, and treatment of acute pain with non-opioid analgesia, nonpharmacologic strategies, and short-acting opioids as needed, are all essential to adequate management of acute pain in patients with OUD. A multidisciplinary approach to treatment and discharge planning in patients with OUD may be beneficial to engage patients with OUD early in their hospital stay to prevent withdrawal, stabilize their OUD, and to reduce the risk of unplanned discharge and other associated morbidity. This article is protected by copyright. All rights reserved.

QT Interval Prolongation in the Pediatric Oncologic Population on Methadone

Studies have been conducted on adults prescribed with methadone to determine the necessary frequency of QTc monitoring but no consensus has been reached and no similar research has been conducted in the pediatric population. The objective of this retrospective study was to determine the occurrence rate of QTc interval prolongation associated with methadone use in a pediatric oncologic population. In total, 18% of patients developed QTc interval prolongation. These patients had longer baseline QTc intervals and were on more QTc interval-prolonging medications. Our data suggest that these variables may be able to risk stratify patients who require more frequent monitoring.

Risk Factors and Prevalence of QTc Prolongation in Adult Burn Patients Receiving Methadone

Methadone is an opioid commonly used for acute pain management in burn patients. One adverse effect of methadone is QTc interval prolongation, which may be associated with adverse cardiac outcomes. There is currently a paucity of data regarding risk of QTc prolongation in burn patients taking methadone and a lack of evidence-based recommendations for monitoring strategies in this population. The study objective was to determine the prevalence, risk factors, and cardiac outcomes related to methadone-associated QTc prolongation in adult burn patients. A total of 91 patients were included and were divided into groups according to maximum QTc. QTc prolongation was defined as greater than or equal to 470 ms (males) or 480 ms (females). There were no differences between groups regarding patient-specific risk factors, baseline QTc, or time to longest QTc. Patients in the prolonged QTc group had a higher rate of cardiac events (44% vs 9%; P < .001), higher median (IQR) change from baseline to longest QTc (61 ms [18,88] vs 23 ms [13,38]; P < .001), higher median (IQR) total daily dose of methadone (90 mg [53,98] vs 53 mg [30,75]; P = .004), and longer median (IQR) length of stay (53 [33,82] vs 35 [26,52] days; P = .008). QTc prolongation in burn patients was associated with increased methadone dose and resulted in a higher rate of cardiac events. This study was the first of its kind to look at risk factors and cardiac outcomes associated with methadone use in burn patients.

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.

Evaluation of QTc Interval Prolongation Among Patients With Cancer Using Enteral Methadone

CONTEXT:

The effect of methadone on corrected QT interval (QTc) in patients with cancer pain is not well-known.

OBJECTIVES:

To describe and characterize the effect of low-, moderate-, and high-dose enteral methadone on QTc interval in patients with cancer.

METHODS:

Retrospective cohort study including patients prescribed enteral methadone during the 27-month study period. Participants were divided into 3 methadone daily dose groups: <30 (low dose), 30 to 59 (moderate dose), ≥60 (high dose) mg. The primary outcome was the incidence of QTc prolongation (>450 ms for females and >430 ms for males). Secondary outcomes included the magnitude of change in QTc after starting methadone, the incidence of clinically significant QTc prolongation (>500 ms) and the prevalence of torsades de pointes and syncope.

RESULTS:

Two hundred three patients met study inclusion criteria: 91 (45%) low dose, 52 (26%) moderate dose, and 60 (29%) high dose. Incidence of QTc prolongation for low-, moderate-, and high-dose groups was 50 (55%), 37 (71%), and 43 (72%), respectively ( P = .039, low vs high dose). Incidence of clinically significant QTc prolongation was 10 (11%), 4 (8%), and 7 (12%) for low-, moderate-, and high-dose groups. For patients without QTc prolongation prior to initiating methadone, 62% of moderate-dose patients and 67% of high-dose patients had QTc prolongation, while taking methadone.

CONCLUSION:

This study found a notably high incidence of QTc prolongation in patients with cancer using enteral methadone. Future studies should aim to determine the risk of adverse cardiac effects in the cancer population and determine appropriate monitoring of methadone for pain management.

Opioids and Cardiac Arrhythmia: A Literature Review

OBJECTIVE

One of the most important side effects of opioids is their influence on the electrical activity of the heart. This review focusses on the effects of opioids on QT interval prolongation and their arrhythmogenic liability.

METHODS

By using various keywords, papers published up to 2018 in different databases were searched and identified. The search terms were opioids names, corrected QT interval, human-ether-a-go-go gene, torsades de pointes (TdP), cardiac arrhythmias, opioid dependence and other relevant terms. It emphasized the effects of each opioid agent alone on electrocardiogram (ECG) and some interactions.

RESULTS

Available data indicate that some opioids such as methadone are high-risk even at low doses, and have potential for prolongation of the QT interval and development of TdP, a dangerous ventricular tachycardia. A number of opioids such as tramadol and oxycodone are intermediate risk drugs and may develop long QT interval and TdP in high doses. Some other opioids such as morphine and buprenorphine are low-risk drugs and do not produce QT interval prolongation and TdP at least in routine doses. Opium-consumers are at higher risk of supra-ventricular arrhythmias, sinus bradycardia, cardiac block and atrial fibrillation.

CONCLUSION

The cardiac arrhythmogenicity of various opioids is different. Methadone has a higher capability to induce long QT interval and dangerous arrhythmias in conventional doses than others. To reduce of arrhythmogenic risk, high doses of opioids must be used cautiously with periodic monitoring of ECG in high-risk consumers such as patients under opioid maintenance treatment.

Methadone and Corrected QT Prolongation in Pain and Palliative Care Patients: A Case-Control Study

BACKGROUND

Methadone (ME) is commonly used in pain and palliative care (PPC) patients with refractory pain or intolerable opioid adverse effects (AEs). A unique ME AE is its corrected QT (QTc) interval prolongation risk, but most evidence exists in methadone maintenance therapy patients.

OBJECTIVE

Our goal was to identify QTc interval prolongation risk factors in PPC patients receiving ME and other medications known to prolong the QTc interval and develop a risk stratification tool.

DESIGN

We performed a case-control study of adult inpatients receiving ME for pain management. Settings/Subjects: Adult inpatients receiving ME with a QTc >470 msec (males) and >480 msec (females) were matched 1:2 according to age, history of QTc prolongation, and gender with ME patients who did not have a prolonged QTc interval. QTc prolongation risk factors were collected for both groups. Covariates were analyzed using conditional logistic regression. Classification and regression tree analysis was used to identify the ME dose associated with QTc prolongation.

RESULTS

Predictors of QTc prolongation included congestive heart failure (CHF) (OR: 11.9; 95% CI: 3.7-38.2; p < 0.00), peptic ulcer disease (PUD) (odds ratio [OR]: 8.3; 95% confidence interval [95% CI]: 2.4-28.9; p < 0.00), hypokalemia (OR: 6.5; 95% CI: 1.5-28.2; p < 0.01), rheumatologic diseases (OR: 4.7; 95% CI: 1.6-13.9; p < 0.00), taking medications with a known torsades de pointes (TdP) risk (OR: 4.4; 95% CI: 1.8-10.7; p < 0.01), malignancy (OR: 3.3; 95% CI: 1.2-9.3; p < 0.03), hypocalcemia (OR: 2.1; 95% CI: 0.9-4.8; p < 0.07), and ME doses >45 mg per day (OR: 1.9; 95% CI: 0.8-4.8; p < 0.16). Mild liver disease was protective against QTc prolongation (OR: 0.05; 95% CI: 0.0-0.46; p < 0.01).

CONCLUSIONS

Predictors of QTc prolongation in our multivariate conditional logistic regression model included CHF, PUD, hypokalemia, rheumatologic disorders, use of medications with a known TdP risk, malignancy, hypocalcemia, and ME doses >45 mg per day.

The Impact of Opioids on Cardiac Electrophysiology

Synthetic opioid agents have been used in modern medicine for over a century and for opioid addiction treatment for over a half-century. Liberal use of opioids in the United States has been attended by an extraordinary increase in opioid-related mortality, with over 16,000 deaths in 2012. As there have been advances in opioid agents for pain and addiction, so have there been advances in our understanding of the cardiac effects of these agents. In the last 10 years, significant data regarding electrophysiologic effects of these agents have been collected. We aim in this review to discuss the effects on cardiac electrophysiology of the various opioid agents currently in use and the evidence that these effects are contributing to the rise in opioid-related mortality.

Methadone analgesia in the critically ill

PURPOSE

Methadone is increasingly used as an analgesic or a bridge to weaning other analgesics and sedatives in critically ill patients. This review discusses the pharmacology of methadone, summarizes available evidence for its use in the intensive care unit setting, and makes suggestions for appropriate use and monitoring.

MATERIALS/METHODS

Articles evaluating the efficacy, safety, and pharmacology of methadone were identified from a PubMed search through June 2015. References from selected articles were reviewed for additional material. Experimental and observational English-language studies that focused on the efficacy, safety, and pharmacology of methadone in critically-ill adults and children were selected.

RESULTS

Methadone is a synthetic opioid analgesic with potential advantages over other commonly used opioids. Limited evidence from critically ill pediatric, adult, and burn populations suggests that methadone protocols may expedite weaning opiate infusions, decrease the length of mechanical ventilation, and reduce the incidence of negative outcomes such as opiate withdrawal, delirium, and over-sedation.

CONCLUSIONS

Data from current literature supports a role for methadone analgesia in weaning opiates and potentially reducing the duration of mechanical ventilation in critically ill patients. More studies are needed to confirm these benefits and determine criteria for patient selection.

Is levorphanol a better option than methadone?

BACKGROUND

Methadone has been a stalwart pharmacologic option for the management of opioid drug dependence for many years. It substitutes for opioid agonists and possesses certain pharmacokinetic properties that confer characteristics preferable to those of other opioids for this application. Methadone is likewise used as an option for the treatment of pain, particularly chronic pain. It has a spectrum of pharmacodynamic activity, including contributions from non-opioid components, that translates to its specific clinical attributes as an analgesic. Unfortunately, basic science studies and accumulated clinical experience with methadone have revealed some undesirable, and even worrisome, features, including issues of safety. The benefit/risk ratio of methadone might be acceptable if there was no better alternative, but neither its pharmacokinetic nor pharmacodynamic properties are unique to methadone.

OBJECTIVE

We review the basic and clinical pharmacology of methadone and suggest that levorphanol should receive attention as a possible alternative.

CONCLUSION

Unlike methadone, levorphanol is a more potent NMDA antagonist, possesses a higher affinity for DOR and KOR, has a shorter plasma half-life yet longer duration of action, has no CYP450 interactions or QTc prolongation risk, can be a viable option in the elderly, palliative care, and SCI patients, requires little to no need for co-administration of adjuvant analgesics, and has potentially a lower risk of drug-related Emergency Department visits compared to other opioids.

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.

The QTc effect of low-dose methadone for chronic pain: a prospective pilot study

OBJECTIVE

Methadone is associated with QT prolongation and serious cardiac complications, but this has been primarily demonstrated in opioid dependent patients receiving moderate to high doses. This study investigates the effect of low-dose methadone on the QTc interval in a chronic pain population.

DESIGN AND SUBJECTS

We conducted a prospective cohort study in a chronic pain clinic including 82 patients receiving methadone and 102 patients receiving non-methadone opioid therapy.

METHODS

We analyzed automated QTc calculations from 12-lead electrocardiograms at baseline and during the subsequent 6 months. The primary outcome of interest was the incidence of QTc greater than 470 milliseconds or an increase from baseline of greater than 60 milliseconds.

RESULTS

The methadone group did not manifest an overall higher frequency of QTc > 470 milliseconds (6% for the methadone group vs 5% for controls, P = 0.722) or an increase in the QTc of > 60 milliseconds (4% for the methadone group vs 4% for controls, P = 0.94). In the first month after initiating methadone, patients demonstrated an increase in QTc compared to controls (5% for the methadone group vs 0% for the controls, P = 0.073) but the difference disappeared in the third and sixth months.

CONCLUSION

Data from our chronic pain clinic support a potential association of QTc prolongation during the initiation of methadone, but this effect is small and short lived. We believe larger scale studies to further characterize the safety profile of low-dose methadone are warranted.

Evaluation of Methadone-Induced QTc Prolongation in a Veteran Population

Understanding the effects of methadone on the QTc interval in a veteran patient population using the drug at lower doses for pain may help clinicians develop strategies and protocols for safe use.

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.

Pain care for patients with epidermolysis bullosa: best care practice guidelines

BACKGROUND

Inherited epidermolysis bullosa (EB) comprises a group of rare disorders that have multi-system effects and patients present with a number of both acute and chronic pain care needs. Effects on quality of life are substantial. Pain and itching are burdensome daily problems. Experience with, and knowledge of, the best pain and itch care for these patients is minimal. Evidence-based best care practice guidelines are needed to establish a base of knowledge and practice for practitioners of many disciplines to improve the quality of life for both adult and pediatric patients with EB.

METHODS

The process was begun at the request of Dystrophic Epidermolysis Bullosa Research Association International (DEBRA International), an organization dedicated to improvement of care, research and dissemination of knowledge for EB patients worldwide. An international panel of experts in pain and palliative care who have extensive experience caring for patients with EB was assembled. Literature was reviewed and systematically evaluated. For areas of care without direct evidence, clinically relevant literature was assessed, and rounds of consensus building were conducted. The process involved a face-to-face consensus meeting that involved a family representative and methodologist, as well as the panel of clinical experts. During development, EB family input was obtained and the document was reviewed by a wide variety of experts representing several disciplines related to the care of patients with EB.

RESULTS

The first evidence-based care guidelines for the care of pain in EB were produced. The guidelines are clinically relevant for care of patients of all subtypes and ages, and apply to practitioners of all disciplines involved in the care of patients with EB. When the evidence suggests that the diagnosis or treatment of painful conditions differs between adults and children, it will be so noted.

CONCLUSIONS

Evidence-based care guidelines are a means of standardizing optimal care for EB patients, whose disease is often times horrific in its effects on quality of life, and whose care is resource-intensive and difficult. The guideline development process also highlighted areas for research in order to improve further the evidence base for future care.

Methadone for pain and the risk of adverse cardiac outcomes

CONTEXT

There are few studies that describe cardiac adverse events in patients prescribed methadone for pain management.

OBJECTIVES

To describe incident cardiac adverse events and risk factors for cardiac adverse events in primary care patients prescribed methadone for pain.

METHODS

This was a retrospective, descriptive, cohort study in patients 18 years or older receiving methadone for pain management during 2010. Patients were followed for 12 months and were categorized as "chronic" or "non-chronic" methadone users. The primary outcomes were a cardiac event, at risk for an event, or neither. Patients were grouped on their outcome and were compared on risk factors and methadone monitoring.

RESULTS

A total of 1246 patients were included. Thirty (2.4%), 628 (50.4%), and 588 (47.2%) patients had a cardiac event, were at risk for an event, or had neither an event nor a risk factor, respectively. Overall, the rate of QTc prolongation was 49.4% and the rate of adherence to recommended cardiac monitoring was 39.0%. Similar percentages of chronic and non-chronic users had a cardiac event (P > 0.05). Among the patients who had a cardiac event and were at risk for an event, factors independently associated with having had an event included age (odds ratio = 1.06; 95% CI = 1.03-1.09) and a dose 100 mg/day or higher (odds ratio = 6.18; 95% CI = 1.08-35.45).

CONCLUSION

Few cardiac adverse events resulting from methadone use for pain were detected. However, a large proportion of patients were at risk for an adverse event, especially patients who were older and had received ≥ 100 mg/day of methadone.

Prognostic factors in acute methadone toxicity: a 5-year study

Background. Delayed or recurrent profound respiratory depression, ventricular dysrhythmias, acute lung injury, and death are the major complications of MTD overdose. We aimed to clarify the prognostic factors in MTD toxicity. Materials and Methods. Retrospectively, medical files of all patients poisoned by MTD and older than 12 years of age who had presented to Loghman Hakim Poison Center between 2007 and 2012 were evaluated. The data was compared between survivors and nonsurvivors. Results. Twenty-eight out of 322 patients died (mortality rate = 8.7%). MTD-related death was higher in patients with acute on chronic toxicity who were on daily dose of MTD and had ingested higher doses (in comparison to those with acute toxicity due to first-time exposure; 13% versus 6%). Renal failure was the most common medical complication related to deaths due to MTD toxicity. Conclusions. Based on previous researches, the most common cause of MTD overdose-related deaths is respiratory impairment; however, in our study, acute renal failure with or without rhabdomyolysis was the main delayed cause of deaths in MTD-poisoned patients. Antidotal therapy, early recognition, and treatment of hemodynamic compromise and rhabdomyolysis can be life-saving in these patients.

Patient considerations in the use of tapentadol for moderate to severe pain

Poorly controlled acute and chronic pain can increase morbidity, impair quality of life and prolong disability. Over 80 percent of post surgical patients report moderate to severe uncontrolled postoperative pain. Over-reliance on potent opioid agonists can lead to several opioid related side effects such as gastrointestinal intolerability, respiratory depression and cognitive impairment. A recently approved dual acting central analgesic tapentadol may offer improved tolerability over traditional opioid agonists while having multimodal opioid and nonopioid analgesic benefits. Tapentadol, classified by the US Food and Drug Administration as a class 2 opioid, is currently marketed in the United States as immediate release (IR) NUCYNTA® for moderate to severe acute pain in tablets of 50 mg, 75 mg, and 100 mg, and as extended release (ER) NUCYNTA ER® for the treatment of chronic moderate to severe pain in tablets of 50 mg, 100 mg, 150 mg, 200 mg, and 250 mg. Tapentadol is a low affinity mu opioid receptor agonist and a norepinephrine reuptake inhibitor. Tapentadol has no active metabolites and this property makes it useful in patients with hepatic and renal failure. Clinical trials with tapentadol IR showed that there was improved gastrointestinal tolerability and similar pain relief as compared to oxycodone IR. Tapentadol ER allows for twice daily dosing. Clinical trials showed that tapentadol ER could effectively relieve moderate to severe chronic pain and was associated with significantly fewer gastrointestinal adverse effects as compared to oxycodone controlled release. Tapentadol ER is indicated and has Food and Drug Administration approval for the treatment of chronic painful diabetic neuropathy. The most common side effects of tapentadol are nausea (30%), vomiting (18%), dizziness (24%), and somnolence (15%). Tapentadol, due to its potential synergistic effects on norepinephrine levels, is contraindicated in patients who have taken monoamine oxidase inhibitors within the last 14 days. Caution has to be exercised with the use of tapentadol IR and tapentadol ER in the presence of other central nervous system depressants such as neuroleptics, opioids, illicit drugs, muscle relaxants, sedatives, and anxiolytics.

QTc interval prolongation for patients in methadone maintenance treatment: a five years follow-up study

BACKGROUND

QTc prolongation for patients in methadone maintenance treatment (MMT) has been reported. In this study we wanted to identify the predictor factors for QTc prolongation >500 ms and other medical risk factors for mortality in this population.

METHODS

A retrospective chart review study with 55 patients who had previously been included in our performance improvement project and who were eligible to be reviewed. A linear regression model with one-sided p value was used for data analysis.

RESULTS

Over 5 years, 41% to 56% of patients had QTc > 450 and <500 ms and 4% to 10% of patients had at least one reading of QTc > 500 ms. This QTc prolongation from baseline showed statistical significance (p < 0.0001). Being diagnosed with congestive heart failure (CHF), elevated HgA1c level and recent cocaine use were significantly associated with QTc prolongation >500 ms. The model as a whole showed statistical significance (F = 3.50, p = 0.02). Being diagnosed with CHF and elevated HgA1c level was significantly associated with mortality. The model as a whole also showed statistical significance (F = 4.63, p = 0.01).

CONCLUSIONS

This study confirms that methadone may be associated with QTc prolongation. It identified three risk factors for significant QTc prolongation for patients on MMT which are recent cocaine use, uncontrolled blood glucose and CHF. Two of these three risk facts (uncontrolled blood glucose and CHF) were associated with mortality in this cohort. Patients with these medical co-morbidities may benefit from EKG screening and aggressive treatment of the medical risk factors while taking MMT.

Increased incidence of QT interval prolongation in a population receiving lower doses of methadone maintenance therapy

AIMS

The aim of this study was to investigate the frequency of corrected QT interval (QTc) prolongation in a methadone maintenance therapy (MMT) population, and to examine potential associations between this QTc interval and methadone dose as well as concurrent use of opiates, cocaine and benzodiazepines.

DESIGN

Cross-sectional study of patients attending a specialist drug treatment clinic from July 2008 to January 2009.

SETTING

Single-centre inner-city specialist drug treatment clinic, Ireland.

PARTICIPANTS

A total of 180 patients on stable MMT attending for daily methadone doses, over a 6-month period, where a total of 376 patients were attending during the study period.

MEASUREMENTS

All patients agreeing to participate in the study underwent 12-lead electrocardiograms and QTc analysis, as well as analysis of urine toxicology screen results for opiates, benzodiazepines and cocaine. ECGs were carried out prior to methadone dose being received, regardless of time of day (trough ECG).

FINDINGS

The average age was 32.6 ± 7.1 years, with mean [standard deviation (SD)] methadone dose 80.4 ± 27.5 mg. The mean (SD) QTc was 420.9 ± 21.1 ms, range 368-495 ms. Patients who had a positive toxicology screen for opiates were receiving significantly lower doses of methadone (77.8 ± 23.5 mg versus 85.0 ± 21.4 mg, P = 0.04). No significant association was noted between QTc interval prolongation and presence of cocaine metabolites in the urine (P = 0.13) or methadone dose (P = 0.33). 8.8% of patients had evidence of prolonged QTc interval (8.3% male QTc ≥ 450 ms and 0.5% female QTc ≥ 470 ms), with 11.1% (n = 20) having QTc intervals > 450 ms.

CONCLUSIONS

Drug-induced corrected QT interval prolongation is evident (ranging from 8.8-11.1%, depending on definition applied) in patients receiving relatively low daily doses of methadone therapy, with no evidence of a dose-response relationship. The presence of cocaine metabolites in urine does not appear to be associated with increased corrected QT interval. Increased awareness of cardiac safety guidelines, including relevant clinical and family history, baseline and trough dose ECG monitoring, should be incorporated into methadone maintenance therapy protocols.

Evaluation of QTc interval in Iranian causalities (Janbazan) of Iran-Iraq war receiving maintenance methadone treatment

BACKGROUND

Methadone is a synthetic opioid, used in treatment of chronic pains. The current study was carried out to evaluate the QTc interval in Iranian causalities (Janbazan) of Iran-Iraq war receiving maintenance methadone treatment.

MATERIALS AND METHODS

In 2010, one hundred war causalities in Isfahan who chronically take daily dose of 20 mg or more of methadone (more than 2 weeks), and did not have the history of cerebrovascular or coronary artery diseases, cardiac pacemaker, congenital prolonged QTC, or taking drugs affecting QTc, or having electrolyte abnormalities, were selected for the study. An electrocardiogram was taken from each patient using cardiofax instrument, and QTC was calculated manually. The data was analyzed using SPSS software with descriptive statistical methods and Pearson's correlation coefficient.

FINDINGS

All patients were male and had the mean age of 45.6 ± 6.1 years. The patients received 20-240 mg methadone daily for 1 to 108 months. The QTc was prolonged in 25% of the patients (QTc 5 450 ms), with the mean of 472.72 ± 18.5 ms (range 450-508 ms) and the mean daily dose of methadone 85.2 ± 59.0 mg. No significant relationship was observed between QTC interval on the one hand, and methadone dose (R = 0.025, P = 0.8), duration of treatment (R =-0.048, P = 0.68), age (R = 0.037, P = 0.71), and weight (R = 0.1, P = 0.21) of the patients, on the other hand. None of the patients had faint, syncope, arrhythmia, or sudden death.

CONCLUSION

Oral methadone causes prolongation of QTC interval. However, the dosage of methadone and duration of treatment were not statistically related to QTC interval.

Low Molecular Weight Opioid Peptide Esters Could be Developed as a New Class of Analgesics

Low molecular weight opioid peptide esters (OPE) could become a class of analgesics with different side effect profiles than current opiates. OPE may have sufficient plasma stability to cross the blood brain barrier (BBB), undergo ester hydrolysis and produce analgesia. OPE of dipeptides, tyr-pro and tyr-gly conjugated to ethanol have a structure similar to the anesthestic agent, etomidate. Based upon the analgesic activity of dipeptide opioids, Lipinski's criteria, and permeability of select GABA esters to cross the BBB, opioid peptides (OP) conjugated to ethanol, cholesterol or 3-glucose are lead recommendations. Preliminary animal data suggests that tyr-pro-ethyl ester crosses the BBB and unexpectedly produces hyperalgesia. Currently, there are no approved OP analgesics available for clinical use. Clinical trials of good manufacturing practice OP administered to patients suffering from chronic pain with indwelling intrathecal pumps could resolve the issue that OP may be superior to opiates and may redirect research.