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

The life and times of endogenous opioid peptides: Updated understanding of synthesis, spatiotemporal dynamics, and the clinical impact in alcohol use disorder

The opioid G-protein coupled receptors (GPCRs) strongly modulate many of the central nervous system structures that contribute to neurological and psychiatric disorders including pain, major depressive disorder, and substance use disorders. To better treat these and related diseases, it is essential to understand the signaling of their endogenous ligands. In this review, we focus on what is known and unknown about the regulation of the over two dozen endogenous peptides with high affinity for one or more of the opioid receptors. We briefly describe which peptides are produced, with a particular focus on the recently proposed possible synthesis pathways for the endomorphins. Next, we describe examples of endogenous opioid peptide expression organization in several neural circuits and how they appear to be released from specific neural compartments that vary across brain regions. We discuss current knowledge regarding the strength of neural activity required to drive endogenous opioid peptide release, clues about how far peptides diffuse from release sites, and their extracellular lifetime after release. Finally, as a translational example, we discuss the mechanisms of action of naltrexone (NTX), which is used clinically to treat alcohol use disorder. NTX is a synthetic morphine analog that non-specifically antagonizes the action of most endogenous opioid peptides developed in the 1960s and FDA approved in the 1980s. We review recent studies clarifying the precise endogenous activity that NTX prevents. Together, the works described here highlight the challenges and opportunities the complex opioid system presents as a therapeutic target.

Use of Contrave, Naltrexone with Bupropion, Bupropion, or Naltrexone and Major Adverse Cardiovascular Events: A Systematic Literature Review

Naltrexone/Bupropion extended release (ER; Contrave) is an extended-release, fixed-dose combination medication of naltrexone (8 mg) and bupropion (90 mg) for patients with obesity or overweight with at least one weight-related comorbidity. Obese and overweight patients with or without comorbidities are at increased cardiovascular (CV) risk. Due to the increased CV risk profile in this patient population, this systematic literature review was conducted to assess human studies reporting major adverse CV events (MACE) and other CV events. A priori eligibility criteria included clinical studies (randomized and observational) published from January 1, 2012, to September 30, 2021, with data comparing users of naltrexone/bupropion ER, naltrexone with bupropion, bupropion without naltrexone, or naltrexone without bupropion versus comparator groups (placebo or other treatments), and with sufficient information to determine the frequency of MACE or other CV adverse events by treatment group. Among 2539 English-language articles identified, 70 articles met the eligibility criteria: seven studies of naltrexone/bupropion ER or naltrexone with bupropion, 32 studies of bupropion, and 31 studies of naltrexone. No studies reported an increased risk of MACE among users of naltrexone/bupropion ER, naltrexone with bupropion, or bupropion or naltrexone individually compared with nonusers. One-half of the available studies (n = 35) reported no (zero) CV events and the other half (n = 35) reported that a non-zero frequency of CV events occurred. Four studies reported data on MACE, including three studies of bupropion and one study of naltrexone/bupropion ER. For composite MACE and its components, the difference in proportions between naltrexone/bupropion ER-, bupropion-, or naltrexone-treated patients compared with active comparators or placebo-treated patients did not exceed 2.5%. In conclusion, the available human evidence does not indicate an increased risk of CV events or MACE following use of naltrexone/bupropion ER, naltrexone with bupropion, or the individual components.

Impact of the Opioid Epidemic

In recent years the prescription opioid overdose epidemic has decreased, but has been more than offset by increases in overdose caused by fentanyl and fentanyl analogues. Opioid overdose patients should receive naloxone if they have significant respiratory depression and/or loss of protective airway reflexes. Patients who receive naloxone should be observed for recurrent opioid effects. Patients with opioid overdose may be admitted to the intensive care unit for naloxone infusions, treatment of noncardiogenic pulmonary edema, autonomic instability, or sequelae of hypoxia-ischemia or cardiac arrest. Primary and secondary prevention are important to reduce the number of people with life-threatening opioid overdose.

Opioid-Associated Out-of-Hospital Cardiac Arrest: Distinctive Clinical Features and Implications for Health Care and Public Responses: A Scientific Statement From the American Heart Association

Opioid overdose is the leading cause of death for Americans 25 to 64 years of age, and opioid use disorder affects >2 million Americans. The epidemiology of opioid-associated out-of-hospital cardiac arrest in the United States is changing rapidly, with exponential increases in death resulting from synthetic opioids and linear increases in heroin deaths more than offsetting modest reductions in deaths from prescription opioids. The pathophysiology of polysubstance toxidromes involving opioids, asphyxial death, and prolonged hypoxemia leading to global ischemia (cardiac arrest) differs from that of sudden cardiac arrest. People who use opioids may also develop bacteremia, central nervous system vasculitis and leukoencephalopathy, torsades de pointes, pulmonary vasculopathy, and pulmonary edema. Emergency management of opioid poisoning requires recognition by the lay public or emergency dispatchers, prompt emergency response, and effective ventilation coupled to compressions in the setting of opioid-associated out-of-hospital cardiac arrest. Effective ventilation is challenging to teach, whereas naloxone, an opioid antagonist, can be administered by emergency medical personnel, trained laypeople, and the general public with dispatcher instruction to prevent cardiac arrest. Opioid education and naloxone distributions programs have been developed to teach people who are likely to encounter a person with opioid poisoning how to administer naloxone, deliver high-quality compressions, and perform rescue breathing. Current American Heart Association recommendations call for laypeople and others who cannot reliably establish the presence of a pulse to initiate cardiopulmonary resuscitation in any individual who is unconscious and not breathing normally; if opioid overdose is suspected, naloxone should also be administered. Secondary prevention, including counseling, opioid overdose education with take-home naloxone, and medication for opioid use disorder, is important to prevent recurrent opioid overdose.

A study of the effectiveness of naltrexone in preventing recurrence of methadone poisoning in opioid-naive children

BACKGROUND

The prevalence of poisoning from methadone and prescription opioids is increasing in pediatric populations. Naloxone is the main antidote for treatment. Long-acting opioid toxicity may need close observation in the intensive care unit (ICU). In our previous study, naltrexone prevented re-narcotization in methadone-poisoned adults. Here, we aim to share our experience with the use of oral naltrexone for preventing recurrence of toxicity in opioid-naïve children.

METHODS

In a single-center, retrospective case series, children (age ≤12 years) admitted to a poison center in Tehran (Iran) between March 2014-March 2016 were included if they presented with methadone poisoning and received naltrexone treatment in hospital. Naltrexone (1 mg/kg) was administrated orally after initial administration of 0.1 mg/kg naloxone intravenously. Children were monitored for level of consciousness, cyanosis, respiratory rate, VBG results, and O2 saturation for ≥48 h during their hospitalization.

RESULTS

Eighty patients with methadone poisoning were enrolled, with median age of three years (range: 0.2-12.0). None involved polysubstance poisoning. Following naltrexone treatment, none experienced recurrent opioid toxicity during hospitalization, and hospital records indicated no readmission within 72-h post-discharge.

CONCLUSION

Oral naltrexone could be a potential substitute for continuous naloxone infusion in methadone-poisoned children and reduce the need for ICU care.

Safety of Naloxone in Opioid-Naïve Methadone Intoxicated Patients; a Case Series Study

INTRODUCTION

Studies have shown that naloxone can cause behavioral changes in naïve normal volunteers. This study aimed to investigate the possible complications of naloxone in methadone-overdosed opioid-naïve patients.

METHODS

In this pilot study, a total number of 20 opioid-naïve methadone-poisoned patients underwent naloxone challenge test to receive naltrexone. 0.2, 0.6, and 1.2 mg doses of naloxone were administered on minutes 0, 5, and 15-20. The patients were followed for 30 minutes after administration of naloxone and monitored for any upsetting signs and symptoms. Patients with clinical opiate withdrawal scale (COWS) lower than 5 were considered not addicted and the severity of patients' symptoms was calculated using subjective opiate withdrawal syndrome (SOWS).

RESULTS

20 patients with mean age of 25.5±8.09 years were evaluated (70% female). Median ingested dose of methadone was 25 mg [IQR; 10 to 50 mg] and mean time interval between ingestion of methadone and naloxone challenge test was 7.1±4.9 hours. Fourteen patients reported some discomfort after administration of a mean dose of 1.7±0.5 mg of naloxone lasting for a maximum of four hours. The most common patients' complaints were headache (45%) followed by nausea (20%), agitation (20%), abdominal pain (20%), and flushing (20%). Two (10%) mentioned severe panic attack and sensation of near-coming death. SOWS significantly correlated with female gender (p = 0.004) and time elapsed post methadone ingestion (p = 0.001).

CONCLUSION

It seems that naloxone is not a completely safe medication even in opioid-naïve patients, and administrating adjusted doses of naloxone even in opioid-naïve methadone intoxicated patients may be logical.

Delay-Dependent Impairments in Memory and Motor Functions After Acute Methadone Overdose in Rats

Methadone is used as a substitution drug for the treatment of opioid dependence and chronic pain. Despite its widespread use and availability, there is a serious concern with respect to the relative safety of methadone. The purpose of this study was to characterize how acute methadone overdose affects the cognitive and motor performance of naïve healthy rats. The methadone overdose was induced by administering an acute toxic dose of methadone (15 mg/kg; ip; the equivalent dose of 80% of LD50) to adolescent rats. Resuscitation using a ventilator pump along with a single dose of naloxone (2 mg/kg; ip) was administered following the occurrence of apnea. The animals which were successfully resuscitated divided randomly into three apnea groups that evaluated either on day 1, 5, or 10 post-resuscitation (M/N-Day 1, M/N-Day 5, and M/N-Day 10 groups) in the Y-maze and novel object memory recognition tasks as well as pole and rotarod tests. The data revealed that a single toxic dose of methadone had an adverse effect on spontaneous behavior. In addition, Recognition memory impairment was observed in the M/N-Day 1, 5, and 10 groups after methadone-induced apnea. Further, descending time in the M/N-Day 5 group increased significantly in comparison with its respective Saline control group. The overall results indicate that acute methadone-overdose-induced apnea produced delay-dependent cognitive and motor impairment. We suggest that methadone poisoning should be considered as a possible cause of delayed neurological disorders, which might be transient, in some types of memory or motor performance in naïve healthy rats.

Suspected Methadone Toxicity: from Hospital to Autopsy Bed

High mortality rates have been reported for methadone in both adults and children. We aimed to determine the pattern of toxicity, possible underlying diseases and treatment challenges in patients referred to our centre with early diagnosis of methadone toxicity and who later died. Medical files of all methadone-poisoned patients who had been admitted to a referral centre of toxicology between March 2011 and March 2016, died during the hospital stay and sent for autopsy to Legal Medicine Organization were retrospectively evaluated. In a total of 94 patients, autopsy findings and laboratory evaluations showed that cause of death was pure methadone toxicity in 57 (60.6%). Other causes of death were ischaemic heart disease in ten, co-ingestions (toxicities including methadone) in eight, brain haemorrhage, multi-organ failure and pneumosepsis (each in four), meningitis/encephalitis in three and head trauma and other toxicities (other than methadone but including an opioid, each in two) patients. Time of cardiopulmonary arrest was significantly different between those with pure methadone toxicity and those who died due to other causes (p = 0.01). Patients who had died due to co-ingestions and other toxicities were younger (p = 0.029) and took more bolus doses of naloxone (p = 0.042). In methadone users, especially in older ages and those with trivial response to naloxone administration, loss of consciousness should not be strictly attributed to methadone toxicity. In such patients, thorough evaluation for other possible causes of loss of consciousness is mandatory.

Characteristics of Methadone Intoxicated Children Presenting to Emergency Department; a Cross Sectional Study

Introduction:

Each year a large number of patients present to emergency departments (EDs) following accidental or intentional poisoning with methadone. This study was designed with the aim of demographic evaluation of methadone poisoning in children presenting to ED and proposing preventive measures to parents and the healthcare system.

Methods:

This cross sectional study was carried out on children under the age of 12 years presenting to ED of a poisoning referral center. Demographic characteristics of the child and parents, cause of poisoning, form of drug consumed, dose consumed, the symptoms of the child on admission, clinical examination, laboratory findings, and final outcome were recorded and reported using descriptive statistics.

Results:

179 cases were studied (59.2% boys). Cause of consumption was accidental in 175 (97.8%) cases and consumed drug dose was unknown in 53 (53.6%) cases. On admission 6 cases were in deep coma, 133 (74.3%) had miotic pupils, and 52 (29.1%) were affected with respiratory apnea and cyanosis. In 132 (73.8%) cases drugs were obtained from unapproved stores and form of drug consumed was syrup in 146 (81.6%) cases. 177 (98.9%) cases were discharged after 2 or3 days and 2 (1.1%) cases died.

Conclusion:

Based on the results of the present study, most cases of methadone poisoning were accidental, in children residing in poor and middle-class areas, with parents who had a low level of education and had obtained the drug from unapproved stores and stored it in improper containers or at improper places. Only 64.8% of the parents were educated regarding drug storage.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.