Naloxone dosing in the era of ultra-potent opioid overdoses: a systematic review

Slow dissociation kinetics of fentanyls and nitazenes correlates with reduced sensitivity to naloxone reversal at the μ-opioid receptor

BACKGROUND AND PURPOSE

Fentanyls and nitazenes are μ-opioid receptor agonists responsible for a large number of opioid overdose deaths. Here, we determined the potency, dissociation kinetics and antagonism by naloxone at the μ receptor of several fentanyl and nitazene analogues, compared to morphine and DAMGO.

EXPERIMENTAL APPROACH

In vitro assays of G protein activation and signalling and arrestin recruitment were performed. AtT20 cells expressing μ receptors were loaded with a membrane potential dye and changes in fluorescence used to determine agonist potency, dissociation kinetics and susceptibility to antagonism by naloxone. BRET experiments were undertaken in HEK293T cells expressing μ receptors to assess Gi protein activation and β-arrestin 2 recruitment.

KEY RESULTS

The apparent rate of agonist dissociation from the μ receptor varied: morphine, DAMGO, alfentanil and fentanyl dissociated rapidly, whereas isotonitazene, etonitazene, ohmefentanyl and carfentanil dissociated slowly. Slowly dissociating agonists were more resistant to antagonism by naloxone. For carfentanil, the slow apparent rate of dissociation was not because of G protein receptor kinase-mediated arrestin recruitment as its apparent rate of dissociation was not increased by inhibition of G protein-coupled receptor kinases (GRKs) with Compound 101. The in vitro relative potencies of fentanyls and nitazenes compared to morphine were much lower than that previously observed in in vivo experiments.

CONCLUSIONS AND IMPLICATIONS

With fentanyls and nitazenes that slowly dissociate from the μ receptor, antagonism by naloxone is pseudo-competitive. In overdoses involving fentanyls and nitazenes, higher doses of naloxone may be required for reversal than those normally used to reverse heroin overdose.

Hazardous Materials from Threats to Safety: Molecularly Imprinted Polymers as Versatile Safeguarding Platforms

Hazards associated with highly dangerous pollutants/contaminants in water, air, and land resources, as well as food, are serious threats to public health and the environment. Thus, it is imperative to detect or decontaminate, as risk-control strategies, the possible harmful substances sensitively and efficiently. In this context, due to their capacity to be specifically designed for various types of hazardous compounds, the synthesis and use of molecularly imprinted polymers (MIPs) have become widespread. By molecular imprinting, affinity sites with complementary shape, size, and functionality can be created for any template molecule. MIPs' unique functions in response to external factors have attracted researchers to develop a broad range of MIP-based sensors with increased sensitivity, specificity, and selectivity of the recognition element toward target hazardous compounds. Therefore, this paper comprehensively reviews the very recent progress of MIPs and smart polymer applications for sensing or decontamination of hazardous compounds (e.g., drugs, explosives, and biological or chemical agents) in various fields from 2020 to 2024, providing researchers with a rapid tool for investigating the latest research status.

A call for compassionate opioid overdose response

High dose and long-acting opioid overdose reversal drugs can precipitate withdrawal in people who are opioid dependent. Products recently brought to market for community use in the United States (US) have drawn international concern because of their increased risk of withdrawal. At the March 18-19, 2024, Compassionate Overdose Response Summit & Naloxone Dosing Meeting, a panel of harm reduction experts issued the following call to action: 1) people who use drugs should be directly involved in decisions regarding the research, development, selection, and distribution of opioid overdose reversal products; 2) regulatory agencies and pharmaceutical manufacturers should carefully consider and communicate the risk and duration of withdrawal associated with higher dose and longer-acting opioid antagonists; 3) take-home naloxone kits should include at least two doses of an intramuscular (IM) product containing 0.4 mg or an intranasal (IN) product containing ≤4 mg; 4) At this time, high dose and long-acting opioid antagonists have no use in acute opioid overdose response; and, 5) overdose response educational materials, instructions on overdose response, and training should emphasize the restoration of breathing, avoiding withdrawal, and compassionate post-overdose support and care. High dose and long-acting opioid overdose reversal drugs were approved without testing for withdrawal and are often aggressively marketed despite decades of evidence from naloxone distribution programs worldwide that the ideal dose of naloxone is one that restores breathing without inducing withdrawal. Government agencies should direct resources to harm reduction programs to make standard dose take-home naloxone products widely available among people who use drugs. Lay bystanders, people who use drugs, their families, and professional first responders can learn and apply a compassionate approach to opioid overdose response.

Comparison of intranasal naloxone and intranasal nalmefene in a translational model assessing the impact of synthetic opioid overdose on respiratory depression and cardiac arrest

Introduction

Using a validated translational model that quantitatively predicts opioid-induced respiratory depression and cardiac arrest, we compared cardiac arrest events caused by synthetic opioids (fentanyl, carfentanil) following rescue by intranasal (IN) administration of the μ-opioid receptor antagonists naloxone and nalmefene.

Methods

This translational model was originally developed by Mann et al. (Clin Pharmacol Ther 2022) to evaluate the effectiveness of intramuscular (IM) naloxone. We initially implemented this model using published codes, reproducing the effects reported by Mann et al. on the incidence of cardiac arrest events following intravenous doses of fentanyl and carfentanil as well as the reduction in cardiac arrest events following a standard 2 mg IM dose of naloxone. We then expanded the model in terms of pharmacokinetic and µ-opioid receptor binding parameters to simulate effects of 4 mg naloxone hydrochloride IN and 3 mg nalmefene hydrochloride IN, both FDA-approved for the treatment of opioid overdose. Model simulations were conducted to quantify the percentage of cardiac arrest in 2000 virtual patients in both the presence and absence of IN antagonist treatment.

Results

Following simulated overdoses with both fentanyl and carfentanil in chronic opioid users, IN nalmefene produced a substantially greater reduction in the incidence of cardiac arrest compared to IN naloxone. For example, following a dose of fentanyl (1.63 mg) producing cardiac arrest in 52.1% (95% confidence interval, 47.3-56.8) of simulated patients, IN nalmefene reduced this rate to 2.2% (1.0-3.8) compared to 19.2% (15.5-23.3) for IN naloxone. Nalmefene also produced large and clinically meaningful reductions in the incidence of cardiac arrests in opioid naïve subjects. Across dosing scenarios, simultaneous administration of four doses of IN naloxone were needed to reduce the percentage of cardiac arrest events to levels that approached those produced by a single dose of IN nalmefene.

Conclusion

Simulations using this validated translational model of opioid overdose demonstrate that a single dose of IN nalmefene produces clinically meaningful reductions in the incidence of cardiac arrest compared to IN naloxone following a synthetic opioid overdose. These findings are especially impactful in an era when >90% of all opioid overdose deaths are linked to synthetic opioids such as fentanyl.

High-dose naloxone formulations are not as essential as we thought

Naloxone is an effective FDA-approved opioid antagonist for reversing opioid overdoses. Naloxone is available to the public and can be administered through intramuscular (IM), intravenous (IV), and intranasal spray (IN) routes. Our literature review investigates the adequacy of two doses of standard IM or IN naloxone in reversing fentanyl overdoses compared to newer high-dose naloxone formulations. Moreover, our initiative incorporates the experiences of people who use drugs, enabling a more practical and contextually-grounded analysis. The evidence indicates that the vast majority of fentanyl overdoses can be successfully reversed using two standard IM or IN dosages. Exceptions include cases of carfentanil overdose, which necessitates ≥ 3 doses for reversal. Multiple studies documented the risk of precipitated withdrawal using ≥ 2 doses of naloxone, notably including the possibility of recurring overdose symptoms after resuscitation, contingent upon the half-life of the specific opioid involved. We recommend distributing multiple doses of standard IM or IN naloxone to bystanders and educating individuals on the adequacy of two doses in reversing fentanyl overdoses. Individuals should continue administration until the recipient is revived, ensuring appropriate intervals between each dose along with rescue breaths, and calling emergency medical services if the individual is unresponsive after two doses. We do not recommend high-dose naloxone formulations as a substitute for four doses of IM or IN naloxone due to the higher cost, risk of precipitated withdrawal, and limited evidence compared to standard doses. Future research must take into consideration lived and living experience, scientific evidence, conflicts of interest, and the bodily autonomy of people who use drugs.

Clinical Pharmacokinetics and Pharmacodynamics of Naloxone

Naloxone is a World Health Organization (WHO)-listed essential medicine and is the first choice for treating the respiratory depression of opioids, also by lay-people witnessing an opioid overdose. Naloxone acts by competitive displacement of opioid agonists at the μ-opioid receptor (MOR). Its effect depends on pharmacological characteristics of the opioid agonist, such as dissociation rate from the MOR receptor and constitution of the victim. Aim of treatment is a balancing act between restoration of respiration (not consciousness) and avoidance of withdrawal, achieved by titration to response after initial doses of 0.4-2 mg. Naloxone is rapidly eliminated [half-life (t1/2) 60-120 min] due to high clearance. Metabolites are inactive. Major routes for administration are intravenous, intramuscular, and intranasal, the latter primarily for take-home naloxone. Nasal bioavailability is about 50%. Nasal uptake [mean time to maximum concentration (Tmax) 15-30 min] is likely slower than intramuscular, as reversal of respiration lag behind intramuscular naloxone in overdose victims. The intraindividual, interindividual and between-study variability in pharmacokinetics in volunteers are large. Variability in the target population is unknown. The duration of action of 1 mg intravenous (IV) is 2 h, possibly longer by intramuscular and intranasal administration. Initial parenteral doses of 0.4-0.8 mg are usually sufficient to restore breathing after heroin overdose. Fentanyl overdoses likely require higher doses of naloxone. Controlled clinical trials are feasible in opioid overdose but are absent in cohorts with synthetic opioids. Modeling studies provide valuable insight in pharmacotherapy but cannot replace clinical trials. Laypeople should always have access to at least two dose kits for their interim intervention.

Metabolic management of accidental intoxication

PURPOSE OF REVIEW

Unintentional intoxication comprises a major chunk of all intoxications. Most patients are in the pediatric age group with another set of patients being the elderly. Substances found to cause accidental intoxication vary from country to country and even within different regions of a country. Frequent reviews of current literature are needed to be abreast of trends.

RECENT FINDINGS

Prescription drugs and household chemicals are major culprits when it comes to accidental intoxication. Acetaminophen, digoxin and metformin are some of the prominent prescription drugs frequently associated with unintentional intoxications. Increasingly alcohol based hand sanitizers are becoming an important etiology of these events, following their increased usage during the COVID-19 pandemic. Pattern recognition to identify class of intoxicant and supportive care including prevention of further absorption and increased excretion are cornerstones of therapy. Antidote when available should be used promptly.

SUMMARY

Knowledge about current epidemiology of accidental intoxications, toxidrome pattern recognition and appropriate antidote usage beside adequate and timely supportive care help in successful management of the unfortunate victim of accidental intoxication.

Factors associated with obtaining prescribed safer supply among people accessing harm reduction services: findings from a cross-sectional survey

BACKGROUND

With growing rates of unregulated drug toxicity death and concerns regarding COVID-19 transmission among people who use drugs, in March 2020, prescribed safer supply guidance was released in British Columbia. This study describes demographic and substance use characteristics associated with obtaining prescribed safer supply and examines the association between last 6-month harm reduction service access and obtaining prescribed safer supply.

METHODS

Data come from the 2021 Harm Reduction Client Survey administered at 17 harm reduction sites across British Columbia. The sample included all who self-reported use of opioids, stimulants, or benzodiazepines in the prior 3 days (N = 491), given active use of these drugs was a requirement for eligibility for prescribed safer supply. The dependent variable was obtaining a prescribed safer supply prescription (Yes vs. No). The primary independent variables were access to drug checking services and access to overdose prevention services in the last 6 months (Yes vs. No). Descriptive statistics (Chi-square tests) were used to compare the characteristics of people who did and did not obtain a prescribed safer supply prescription. Multivariable logistic regression models were run to examine the association of drug checking services and overdose prevention services access with obtaining prescribed safer supply.

RESULTS

A small proportion (n = 81(16.5%)) of the sample obtained prescribed safer supply. After adjusting for gender, age, and urbanicity, people who reported drug checking services access in the last 6 months had 1.67 (95% CI 1.00-2.79) times the odds of obtaining prescribed safer supply compared to people who had not contacted these services, and people who reported last 6 months of overdose prevention services access had more than twice the odds (OR 2.08 (95% CI 1.20-3.60)) of prescribed safer supply access, compared to people who did not access these services.

CONCLUSIONS

Overall, the proportion of respondents who received prescribed safer supply was low, suggesting that this intervention is not reaching all those in need. Harm reduction services may serve as a point of contact for referral to prescribed safer supply. Additional outreach strategies and service models are needed to improve the accessibility of harm reduction services and of prescribed safer supply in British Columbia.

Systematic Review of Naloxone Dosing and Adverse Events in the Emergency Department

BACKGROUND

Experts recommend using the lowest effective dose of naloxone to balance the reversal of opioid-induced respiratory depression and avoid precipitated opioid withdrawal, however, there is no established dosing standards within the emergency department (ED).

OBJECTIVES

The aim of this review was to determine current naloxone dosing practice in the ED and their association with adverse events.

METHODS

We conducted a systematic review by searching PubMed, Cochrane, Embase, and EBSCO from 2000-2021. Articles containing patient-level data for initial ED dose and patient outcome had data abstracted by two independent reviewers. Patients were divided into subgroups depending on the initial dose of i.v. naloxone: low dose ([LD], < 0.4 mg), standard dose ([SD], 0.4-2 mg), or high dose ([HD], > 2 mg). Our outcomes were the dose range administered and adverse events per dose. We compared groups using chi-squared difference of proportions or Fisher's exact test.

RESULTS

The review included 13 articles with 209 patients in the results analysis: 111 patients in LD (0.04-0.1 mg), 95 in SD (0.4-2 mg), and 3 in HD (4-12 mg). At least one adverse event was reported in 37 SD patients (38.9%), compared with 14 in LD (12.6%, p < 0.0001) and 2 in HD (100.0%, p = 0.16). At least one additional dose was administered to 53 SD patients (55.8%), compared with 55 in LD (49.5%, p < 0.0001), and 3 in HD (100.0%, p = 0.48).

CONCLUSIONS

Lower doses of naloxone in the ED may help reduce related adverse events without increasing the need for additional doses. Future studies should evaluate the effectiveness of lower doses of naloxone to reverse opioid-induced respiratory depression without causing precipitated opioid withdrawal.

High-Dose Naloxone Formulations Are Not as Essential as We Thought

Naloxone is a U.S. Food and Drug Administration (FDA) approved opioid antagonist for reversing opioid overdoses. Naloxone is available to the public, and can be administered through intramuscular (IM), intravenous (IV), and intranasal spray (IN) routes. Our literature review aimed to improve understanding regarding the adequacy of the regularly distributed two doses of low-dose IM or IN naloxone in effectively reversing fentanyl overdoses and whether high-dose naloxone formulations (HDNF) formulations are an optimal solution to this problem. Moreover, our initiative incorporated the perspectives and experiences of people who use drugs (PWUD), enabling a more practical and contextually-grounded analysis. We began by discussing the knowledge and perspectives of Tennessee Harm Reduction, a small peer-led harm reduction organization. A comprehensive literature review was then conducted to gather relevant scholarly works on the subject matter. The evidence indicates that, although higher doses of naloxone have been administered in both clinical and community settings, the vast majority of fentanyl overdoses can be successfully reversed using standard IM dosages with the exception of carfentanil overdoses and other more potent fentanyl analogs, which necessitate three or more doses for effective reversal. Multiple studies documented the risk of precipitated withdrawal using high doses of naloxone. Notably, the possibility of recurring overdose symptoms after resuscitation exists, contingent upon the half-life of the specific opioid. Considering these findings and the current community practice of distributing multiple doses, we recommend providing at least four standard doses of IN or IM naloxone to each potential bystander, and training them to continue administration until the recipient achieves stability, ensuring appropriate intervals between each dose. Based on the evidence, we do not recommend HDNF in the place of providing four doses of standard naloxone due to the higher cost, risk of precipitated withdrawal and limited evidence compared to standard IN and IM. All results must be taken into consideration with the inclusion of the lived experiences, individual requirements, and consent of PWUD as crucial factors. It is imperative to refrain from formulating decisions concerning PWUD in their absence, as their participation and voices should be integral to the decision-making process.

Public health and medical preparedness for mass casualties from the deliberate release of synthetic opioids

The large amounts of opioids and the emergence of increasingly potent illicitly manufactured synthetic opioids circulating in the unregulated drug supply in North America and Europe are fueling not only the ongoing public health crisis of overdose deaths but also raise the risk of another type of disaster: deliberate opioid release with the intention to cause mass harm. Synthetic opioids are highly potent, rapidly acting, can cause fatal ventilatory depression, are widely available, and have the potential to be disseminated for mass exposure, for example, if effectively formulated, via inhalation or ingestion. As in many other chemical incidents, the health consequences of a deliberate release of synthetic opioid would manifest quickly, within minutes. Such an incident is unlikely, but the consequences could be grave. Awareness of the risk of this type of incident and preparedness to respond are required to save lives and reduce illness. Coordinated planning across the entire local community emergency response system is also critical. The ability to rapidly recognize the opioid toxidrome, education on personal protective actions, and training in medical management of individuals experiencing an opioid overdose are key components of preparedness for an opioid mass casualty incident.

The anomalous pharmacology of fentanyl

Fentanyl is a key therapeutic, used in anaesthesia and pain management. It is also increasingly used illicitly and is responsible for a large and growing number of opioid overdose deaths, especially in North America. A number of factors have been suggested to contribute to fentanyl's lethality, including rapid onset of action, in vivo potency, ligand bias, induction of muscle rigidity and reduced sensitivity to reversal by naloxone. Some of these factors can be considered to represent 'anomalous' pharmacological properties of fentanyl when compared with prototypical opioid agonists such as morphine. In this review, we examine the nature of fentanyl's 'anomalous' properties, to determine whether there is really a pharmacological basis to support the existence of such properties, and also discuss whether such properties are likely to contribute to overdose deaths involving fentanyls. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

Mechanisms of Neurorespiratory Toxicity Induced by Fentanyl Analogs—Lessons from Animal Studies

In 2020, fentanyl and its analogs contributed to ~65% of drug-attributed fatalities in the USA, with a threatening increasing trend during the last ten years. These synthetic opioids used as potent analgesics in human and veterinary medicine have been diverted to recreational aims, illegally produced and sold. Like all opioids, central nervous system depression resulting from overdose or misuse of fentanyl analogs is characterized clinically by the onset of consciousness impairment, pinpoint miosis and bradypnea. However, contrasting with what observed with most opioids, thoracic rigidity may occur rapidly with fentanyl analogs, contributing to increasing the risk of death in the absence of immediate life support. Various mechanisms have been proposed to explain this particularity associated with fentanyl analogs, including the activation of noradrenergic and glutamatergic coerulospinal neurons and dopaminergic basal ganglia neurons. Due to the high affinities to the mu-opioid receptor, the need for more elevated naloxone doses than usually required in morphine overdose to reverse the neurorespiratory depression induced by fentanyl analogs has been questioned. This review on the neurorespiratory toxicity of fentanyl and analogs highlights the need for specific research focused on these agents to better understand the involved mechanisms of toxicity and develop dedicated strategies to limit the resulting fatalities.

Importance of Analyzing Intervals to Emergency Medical Service Treatments

BACKGROUND

Although most US emergency medical services (EMS) systems collect time-to-treatment data in their electronic prehospital patient care reports (PCRs), analysis of these data seldom appears in publications. We believe EMS agencies should routinely analyze the initial time-to-treatment data for various potentially life-threatening conditions. This not only assures that protocol-required treatments have been provided but can discover avoidable delays and drive protocol/treatment priority change. Our study purpose was to analyze the interval from 9-1-1 call receipt until the first administration of naloxone to adult opioid overdose victims to demonstrate the quality assurance importance of analyzing time-to-treatment data.

METHODS

Retrospective analysis of intervals from 9-1-1 call receipt to initial naloxone treatment in adult opioid overdose victims. We excluded victims <18 years of age and cases where a bystander, police, or a health care worker gave naloxone before EMS arrival. We compared data collected before and during the COVID-19 pandemic to determine its effect on the analysis.

RESULTS

The mean patient age of 582 opioid overdose victims was 40.7 years [95% CI 39.6, 41.8] with 405 males (69.6%). EMS units' scene arrival was 6.7 minutes from the 9-1-1 call receipt. It took 1.8 minutes to reach the victim, and 8.6 additional minutes to administer the first naloxone regardless of administration route (70.4% intravenous, 26.1% intranasal, 2.7% intraosseous, 0.7% intramuscular). EMS personnel administered the first naloxone 17.1 minutes after the 9-1-1 call receipt, with 50.3% of the delay occurring after patient contact. There was no statistically significant difference in the times-to-treatment before vs. during the pandemic.

CONCLUSION

The prepandemic interval from 9-1-1 call receipt until initial EMS administration of naloxone was substantial and did not change significantly during COVID-19. Our findings exemplify why EMS agencies should analyze initial time-to-treatment data, especially for life-threatening conditions, beyond assuring that protocol-required treatments have been provided. Based on our analysis, fire department crews now carry intranasal naloxone, and intranasal naloxone is given to "impaired" opioid overdose victims the first-arriving fire department or EMS personnel. We continue to collect data on intervals-to-treatment prospectively and monitor our critical process/treatment intervals using the plan-do-study-act model to improve our process/carry out change, and publish our results in a future publication.

Out-of-hospital management of unresponsive, apneic, witnessed opioid overdoses: a case series from a supervised consumption site

OBJECTIVES

There are conflicting recommendations for lay rescuer management of patients who are unresponsive and apneic due to opioid overdose. We evaluated the management of such patients at an urban supervised consumption site.

METHODS

At a single urban supervised consumption site in Vancouver, BC, we conducted a retrospective chart review and administrative database linkage of consecutive patients who were unresponsive and apneic following witnessed opioid overdose between January 1, 2012 and December 31, 2017. We linked these visits with regional hospital records to define the entire care episode, which concluded when the patient was discharged from the supervised consumption site, ED, or hospital, or died. The primary outcome was successful resuscitation, defined as alive and neurologically intact (ambulatory and speaking coherently, or alert and oriented, or Glasgow Coma Scale 15) at the conclusion of the care episode. Secondary outcomes included mortality and predefined complications of resuscitation.

RESULTS

We collected 767 patients, with a median age of 43 and 81.6% male, with complete follow-up on 763 patients (99.5%). All patients were managed with oxygen and ventilation (100%, 95% CI 0.995-1.0); 715 (93.2%, 95% CI 0.911-0.949) received naloxone; no patients underwent chest compressions (0%, 95% CI 0-0.005). All patients with complete follow-up were alive and neurologically intact at the end of their care episode (100%, 95% CI 0.994-1.0). Overall, 191 (24.9%) patients were transported to hospital, and 15 (2.0%) patients required additional naloxone after leaving the supervised consumption site; 16 (2.1%) developed complications, and 1 patient was admitted to hospital.

CONCLUSIONS

At an urban supervised consumption site, all unresponsive, apneic patients with witnessed opioid overdose were successfully resuscitated with oxygen and/or naloxone. No patients required chest compressions.

Epidural electrical stimulation of the cervical spinal cord opposes opioid-induced respiratory depression

Opioid overdose suppresses brainstem respiratory circuits, causes apnoea and may result in death. Epidural electrical stimulation (EES) at the cervical spinal cord facilitated motor activity in rodents and humans, and we hypothesized that EES of the cervical spinal cord could antagonize opioid-induced respiratory depression in humans. Eighteen patients requiring surgical access to the dorsal surface of the spinal cord between C2 and C7 received EES or sham stimulation for up to 90 s at 5 or 30 Hz during complete (OFF-State) or partial suppression (ON-State) of respiration induced by remifentanil. During the ON-State, 30 Hz EES at C4 and 5 Hz EES at C3/4 increased tidal volume and decreased the end-tidal carbon dioxide level compared to pre-stimulation control levels. EES of 5 Hz at C5 and C7 increased respiratory frequency compared to pre-stimulation control levels. In the OFF-State, 30 Hz cervical EES at C3/4 terminated apnoea and induced rhythmic breathing. In cadaveric tissue obtained from a brain bank, more neurons expressed both the neurokinin 1 receptor (NK1R) and somatostatin (SST) in the cervical spinal levels responsive to EES (C3/4, C6 and C7) compared to a region non-responsive to EES (C2). Thus, the capacity of cervical EES to oppose opioid depression of respiration may be mediated by NK1R+/SST+ neurons in the dorsal cervical spinal cord. This study provides proof of principle that cervical EES may provide a novel therapeutic approach to augment respiratory activity when the neural function of the central respiratory circuits is compromised by opioids or other pathological conditions. KEY POINTS: Epidural electrical stimulation (EES) using an implanted spinal cord stimulator (SCS) is an FDA-approved method to manage chronic pain. We tested the hypothesis that cervical EES facilitates respiration during administration of opioids in 18 human subjects who were treated with low-dose remifentanil that suppressed respiration (ON-State) or high-dose remifentanil that completely inhibited breathing (OFF-State) during the course of cervical surgery. Dorsal cervical EES of the spinal cord augmented the respiratory tidal volume or increased the respiratory frequency, and the response to EES varied as a function of the stimulation frequency (5 or 30 Hz) and the cervical level stimulated (C2-C7). Short, continuous cervical EES restored a cyclic breathing pattern (eupnoea) in the OFF-State, suggesting that cervical EES reversed the opioid-induced respiratory depression. These findings add to our understanding of respiratory pattern modulation and suggest a novel mechanism to oppose the respiratory depression caused by opioids.

Real-world study of multiple naloxone administration for opioid overdose reversal among bystanders

Background

The increasing prevalence of highly potent, illicitly manufactured fentanyl and its analogues (IMF) in the USA is exacerbating the opioid epidemic which has worsened during the COVID-19 pandemic. Narcan® (naloxone HCl) Nasal Spray has been approved by the US Food and Drug Administration as a treatment for opioid-related overdoses. Due to the high potency of IMF, multiple naloxone administrations (MNA) may be needed per overdose event. It is essential to determine the patterns of naloxone use, including MNA, and preferences among bystanders who have used naloxone for opioid overdose reversal.

Methods

A cross-sectional web-based survey was administered to 125 adult US residents who administered 4 mg Narcan® Nasal Spray during an opioid overdose in the past year. The survey asked about the most recent overdose event, the use of Narcan® during the event and the associated withdrawal symptoms, and participant preferences regarding dosages of naloxone nasal spray. An open-ended voice survey was completed by 35 participants.

Results

Participants were mostly female (70%) and white (78%), while reported overdose events most frequently occurred in people who were males (54%) and white (86%). Most events (95%) were successfully reversed, with 78% using ≥ 2 doses and 30% using ≥ 3 doses of Narcan® Nasal Spray. Over 90% were worried that 1 Narcan® box may not be enough for a successful future reversal. Reported withdrawal symptoms were similar in overdose events where 1 versus ≥ 2 sprays were given. Eighty-six percent of participants reported more confidence in an 8 mg versus a 4 mg naloxone nasal spray and 77% reported a stronger preference for 8 mg over 4 mg.

Conclusions

MNA occurred in most overdose events, often involving more sprays than are provided in one Narcan® nasal spray box, and participants predominantly expressed having a stronger preference for and confidence in an 8 mg compared to a 4 mg nasal spray. This suggests the need and desire for a higher dose naloxone nasal spray formulation option. Given that bystanders may be the first to administer naloxone to someone experiencing an opioid overdose, ensuring access to an adequate naloxone supply is critical in addressing the opioid overdose epidemic.

Real-world study of multiple naloxone administrations for opioid overdose reversal among emergency medical service providers

Background: The increasing rates of highly potent, illicit synthetic opioids (i.e., fentanyl) in the US is exacerbating the ongoing opioid epidemic. Multiple naloxone administrations (MNA) may be required to successfully reverse opioid overdoses. We conducted a real-world study to assess the rate of MNA for opioid overdose and identify factors associated with MNA. Methods: Data from the 2015-2020 National Emergency Medical Services Information System was examined to determine trends in events requiring MNA. Logistic regression analysis was performed to determine factors associated with MNA. Results: The percentage of individuals receiving MNA increased from 18.4% in 2015 to 28.4% in 2020. The odds of an event requiring MNA significantly increased by 11% annually. The adjusted odds ratio (aOR) for MNA were greatest among males, when advanced life support (ALS) was provided, and when the dispatch complaint indicated there was a drug poisoning event. Conclusions: The 54% increase in MNA since 2015 parallels the rise in overdose deaths attributable to synthetic opioids. This growth is visible in all regions of the country, including the West, where the prevalence of illicitly manufactured synthetic opioids is intensifying. Given this phenomenon, higher naloxone formulations may fulfill an unmet need in addressing the opioid overdose crisis.

The need for multiple naloxone administrations for opioid overdose reversals: A review of the literature

Background A growing challenge in the opioid epidemic is the rise of highly potent synthetic opioids, (i.e., illicitly manufactured fentanyl [IMF]) entering the US non-prescription opioid market. Successful reversal may require multiple doses of naloxone, the standard of care for opioid overdose. We conducted a narrative literature review to summarize the rates of multiple naloxone administrations (MNA) for opioid overdose reversal. Methods: A MEDLINE search was conducted for published articles using MESH search terms: opioid overdose, naloxone and multiple naloxone administration. Of the 2,101 studies identified, articles meeting inclusion/exclusion criteria were reviewed, categorized by primary and secondary outcomes of interest and summarized by data source and study design. Results: A total of 24 articles meeting eligibility criteria were included. Among EMS-based studies, MNA rates ranged from 9% to 53%; in general, bystander-reported studies were notably higher, from 16% to 89%. Variation in study design, data sources, year and geography, may have contributed to these ranges. Three studies that included longitudinal results reported a significant percent increase between 26% and 43% in annual MNA rates or a significant increase in mean naloxone doses over time (p < .001). Conclusions: This summary found that multiple naloxone administrations during opioid overdose encounters vary widely, have occurred in up to 89% of all opioid overdoses, and have significantly increased over time. Higher naloxone formulations may fulfill an unmet need in opioid overdose reversals, given the rising rates of overdoses involving IMF. Further studies are needed to gain a better understanding of MNA during opioid overdose encounters, particularly across a wider geographic region in the US in order to inform continuing efforts to combat the opioid epidemic.

Shifting North American drug markets and challenges for the system of care

Drug markets are dynamic systems which change based on demand, competition, legislation and revenue. Shifts that are not met with immediate and appropriate responses from the healthcare system can lead to public health crises with tragic levels of morbidity and mortality, as experienced Europe in the early 1990s and as is the case in North America currently. The major feature of the current drug market shift in North America is towards highly potent synthetic opioids such as fentanyl and fentanyl analogues. An additional spike in stimulant use further complicates this issue. Without understanding the ever-changing dynamics of drug markets and consequent patterns of drug use, the healthcare system will continue to be ineffective in its response, and morbidity and mortality will continue to increase. Economic perspectives are largely neglected in research and clinical contexts, but better treatment alternatives need to consider the large-scale macroeconomic conditions of drug markets as well as the behavioural economics of individual substance use. It is important for policy makers, health authorities, first responders and medical providers to be aware of the clinical implications of drug market changes in order to best serve people who use drugs. Only with significant clinical research, a comprehensive reorganization of the system of care across all sectors, and an evidence-driven governance, will we be successful in addressing the challenges brought on by the recent shifts in drug markets.

Adverse events related to bystander naloxone administration in cases of suspected opioid overdose in British Columbia: An observational study

Introduction

Take-Home Naloxone programs have been introduced across North America in response to rising opioid overdose deaths. There is currently limited real-world data on bystander naloxone administration, overdose outcomes, and evidence related to adverse events following bystander naloxone administration.

Methods

The research team used descriptive statistics from Take-Home Naloxone administration forms. We explored reported demographic variables and adverse events among people who received by-stander administered naloxone in a suspected opioid overdose event between August 31, 2012 and December 31, 2018 in British Columbia. We examined and contextualized differences across years given policy, program and drug toxicity changes. We used multivariate logistic regression to examine whether an association exists between number of ampoules of naloxone administered and the odds that the recipient will experience withdrawal symptoms.

Results

A large majority (98.1%) of individuals who were administered naloxone survived their overdose and 69.2% had no or only mild withdrawal symptoms. Receiving three (Adjusted Odds Ratio (AOR) 1.64 (95% Confidence Interval (CI): 1.08–2.48)) or four or more (AOR 2.19 (95% CI: 1.32–3.62)) ampoules of naloxone was significantly associated with odds of moderate or severe withdrawal compared to receiving one ampoule of naloxone.

Conclusions

This study provides evidence from thousands of bystander reversed opioid overdoses using Take-Home Naloxone kits in British Columbia, and suggests bystander-administered naloxone is safe and effective for opioid overdose reversal. Data suggests an emphasis on titration during bystander naloxone training in situations where the person experiencing overdose can be adequately ventilated may help avoid severe withdrawal symptoms. We identified a decreasing trend in the likelihood of moderate or severe withdrawal over the study period.

Take-home naloxone programs for suspected opioid overdose in community settings: a scoping umbrella review

BACKGROUND

Opioid related overdoses and overdose deaths continue to constitute an urgent public health crisis. The implementation of naloxone programs, such as 'take-home naloxone' (THN), has emerged as a key intervention in reducing opioid overdose deaths. These programs aim to train individuals at risk of witnessing or experiencing an opioid overdose to recognize an opioid overdose and respond with naloxone. Naloxone effectively reverses opioid overdoses on a physiological level; however, there are outstanding questions on community THN program effectiveness (adverse events, dosing requirements, dose-response between routes of administration) and implementation (accessibility, availability, and affordability). The objective of this scoping review is to identify existing systematic reviews and best practice guidelines relevant to clinical and operational guidance on the distribution of THN.

METHODS

Using the Arksey & O'Malley framework for scoping reviews, we searched both academic literature and grey literature databases using keywords (Naloxone) AND (Overdose) AND (Guideline OR Review OR Recommendation OR Toolkit). Only documents which had a structured review of evidence and/or provided summaries or recommendations based on evidence were included (systematic reviews, meta-analyses, scoping reviews, short-cut or rapid reviews, practice/clinical guidelines, and reports). Data were extracted from selected evidence in two key areas: (1) study identifiers; and (2) methodological characteristics.

RESULTS

A total of 47 articles met inclusion criteria: 20 systematic reviews; 10 grey literature articles; 8 short-cut or rapid reviews; 4 scoping reviews; and 5 other review types (e.g. mapping review and comprehensive reviews). The most common subject themes were: naloxone effectiveness, safety, provision feasibility/acceptability of naloxone distribution, dosing and routes of administration, overdose response after naloxone administration, cost-effectiveness, naloxone training and education, and recommendations for policy, practice and gaps in knowledge.

CONCLUSIONS

Several recent systematic reviews address the effectiveness of take-home naloxone programs, naloxone dosing/route of administration, and naloxone provision models. Gaps remain in the evidence around evaluating cost-effectiveness, training parameters and strategies, and adverse events following naloxone administration. As THN programs continue to expand in response to opioid overdose deaths, this review will contribute to understanding the evidence base for policy and THN program development and expansion.

A qualitative study of repeat naloxone administrations during opioid overdose intervention by people who use opioids in New York City

BACKGROUND

Take-home naloxone (THN) kits have been designed to provide community members (including people who use drugs, their families and/or significant others) with the necessary resources to address out-of-hospital opioid overdose events. Kits typically include two doses of naloxone. This 'twin-pack' format means that lay responders need information on how to use each dose. Advice given tends to be based on dosage algorithms used by medical personnel. However, little is currently known about how and why people who use drugs, acting as lay responders, decide to administer the second dose contained within single THN kits. The aim of this article is to explore this issue.

METHODS

Data were generated from a qualitative semi-structured interview study that was embedded within a randomised controlled trial examining the risks and benefits of Overdose Education and Naloxone Distribution (OEND) training in New York City (NYC). Analysis for this article focuses upon the experiences of 22 people who use(d) opioids and who provided repeat naloxone administrations (RNA) during 24 separate overdose events. The framework method of analysis was used to compare the time participants believed had passed between each naloxone dose administered ('subjective response interval') with the 'recommended response interval' (2-4 minutes) given during OEND training. Framework analysis also charted the various reasons and rationale for providing RNA during overdose interventions.

RESULTS

When participants' subjective response intervals were compared with the recommended response interval for naloxone dosing, three different time periods were reported for the 24 overdose events: i. 'two doses administered in under 2 minutes' (n = 10); ii. 'two doses administered within 2-4 minutes' (n = 7), and iii. 'two doses administered more than 4 minutes apart' (n = 7). A variety of reasons were identified for providing RNA within each of the three categories of response interval. Collectively, reasons for RNA included panic, recognition of urgency, delays in retrieving naloxone kit, perceptions of recipients' responsiveness/non-responsiveness to naloxone, and avoidance of Emergency Response Teams (ERT).

CONCLUSION

Findings suggest that decision-making processes by people who use opioids regarding how and when to provide RNA are influenced by factors that relate to the emergency event. In addition, the majority of RNA (17/24) occurred outside of the recommended response interval taught during OEND training. These findings are discussed in terms of evidence-based intervention and 'evidence-making intervention' with suggestions for how RNA guidance may be developed and included within future/existing models of OEND training.

Steep increases in fentanyl-related mortality west of the Mississippi River: Recent evidence from county and state surveillance

BACKGROUND

Overdose deaths from synthetic opioids (e.g., fentanyl) increased 10-fold in the United States from 2013 to 2018, despite such opioids being rare in illicit drug markets west of the Mississippi River. Public health professionals have feared a "fentanyl breakthrough" in western U.S. drug markets could further accelerate overdose mortality. We evaluated the number and nature of western U.S. fentanyl deaths using the most recent data available.

METHODS

We systematically searched jurisdictions west of the Mississippi River for publicly available data on fentanyl-related deaths since 2018, the most recent Centers for Disease Control and Prevention (CDC) statistics. Using mortality data from 2019 and 2020, we identified changes in fentanyl-related mortality rate and proportion of fatal heroin-, stimulant, and prescription pill overdoses involving fentanyl.

RESULTS

Seven jurisdictions had publicly available fentanyl death data through December 2019 or later: Arizona; California; Denver County, CO; Harris County, TX; King County, WA; Los Angeles County, CA; and Dallas-Fort Worth, TX (Denton, Johnson, Parker, and Tarrant counties). All reported increased fentanyl deaths over the study period. Their collective contribution to national synthetic narcotics mortality increased 371 % from 2017 to 2019. Available 2020 data shows a 63 % growth in fentanyl-mortality over 2019. Fentanyl-involvement in heroin, stimulant, and prescription pill deaths has substantially grown.

DISCUSSION

Fentanyl has spread westward, increasing deaths in the short-term and threatening to dramatically worsen the nation's already severe opioid epidemic in the long-term. Increasing the standard dose of naloxone, expanding Medicaid, improving coverage of addiction treatment, and public health educational campaigns should be prioritized.

Factors associated with withdrawal symptoms and anger among people resuscitated from an opioid overdose by take-home naloxone: Exploratory mixed methods analysis

INTRODUCTION

Take-home naloxone (THN) is a clinically effective and cost-effective means of reducing opioid overdose fatality. Nonetheless, naloxone administration that successfully saves a person's life can still produce undesirable and harmful effects.

AIM

To better understand factors associated with two widely reported adverse outcomes following naloxone administration; namely the person resuscitated displays: i. withdrawal symptoms and ii. anger.

METHODS

A mixed methods study combining a randomized controlled trial of overdose education and naloxone prescribing to people with opioid use disorder and semi-structured qualitative interviews with trial participants who had responded to an overdose whilst in the trial. All data were collected in New York City (2014-2019). A dataset (comprising demographic, pharmacological, situational, interpersonal, and overdose training related variables) was generated by transforming qualitative interview data from 47 overdose events into dichotomous variables and then combining these with quantitative demographic and overdose training related data from the main trial. Associations between variables within the dataset and reports of: i. withdrawal symptoms and ii. anger were explored using chi-squared tests, t-tests, and logistic regressions.

RESULTS

A multivariate logistic regression found that people who had overdosed were significantly more likely to display anger if the person resuscitating them criticized, berated or chastised them during resuscitation (adjusted OR = 27 [95% CI = 4.0-295]). In contrast, they were significantly less likely to display anger if the person resuscitating them communicated positively with them (OR = 0.10 [95% CI = 0.01-0.78]). Both positive and negative communication styles were independently associated with anger, and communication was associated with 59% of the variance in anger. There was no evidence that people who displayed withdrawal symptoms were more likely to display anger than those not displaying withdrawal symptoms, and neither displaying withdrawal symptoms nor displaying anger were associated with using more drugs after resuscitation.

CONCLUSIONS

Contrary to common assumptions, withdrawal symptoms and anger following naloxone administration may be unrelated phenomena. Findings are consistent with previous research that has suggested that a lay responder's positive or reassuring communication style may lessen anger post overdose. Implications for improving THN programmes and naloxone administration are discussed.

Novel Oral Nanoparticle Formulation of Sustained Release Naloxone with Mild Withdrawal Symptoms in Mice

Chronic use of opioids can lead to tolerance, dependence, abuse, and addiction. This in turn can result in dose escalation and opioid overdose. Opioid overdose can be fatal due to severe opioid-induced respiratory depression (OIRD). Naloxone, a nonspecific antagonist of the mu-opioid receptors, is used for the reversal of OIRD. However, one of the major challenges of using naloxone is its short elimination half-life, which is significantly shorter compared to many opioid analgesics. Thus, renarcotization and rapid return to full respiratory depression might occur, specifically in individuals who have taken large doses or long-acting opioid formulations. Additionally, because of the very low oral bioavailability of naloxone, an oral formulation is not currently available. This study examines in mice a novel oral formulation of naloxone based on polymer nanoparticles (NP-naloxone). A single dose of 1 or 5 mg/kg NP-naloxone was highly effective at inhibiting the activating effects of repeated administration of 10 mg/kg morphine for at least up to 24 h. Onset of action was approximately 5 min. Reversal of morphine-induced locomotion was already detected within 1 min and a full effect of returning to baseline activity levels was observed within 5 min. Importantly, at 1 mg/kg, NP-naloxone precipitated very minimal withdrawal behaviors. At the 5 mg/kg dose, NP-naloxone precipitated approximately 40% of the jumping withdrawal behaviors of injectable naloxone. Thus, this study demonstrates that orally administered naloxone based on polymer nanoparticles has high potential to be developed to circumvent OIRD and withdrawal symptoms.

Opioid overdose reversals using naloxone in New York City by people who use opioids: Implications for public health and overdose harm reduction approaches from a qualitative study

BACKGROUND

Adverse reactions to naloxone, such as withdrawal symptoms and aggression, are widely recognised in the literature by pharmaceutical manufacturers and clinical practitioners as standard reactions of individuals who are physically dependent upon opioid drugs following the reversal of potentially fatal opioid overdose. This paper seeks to provide a differentiated view on reactions to naloxone that may have important implications for public health and harm reduction approaches.

METHODS

Analyses from a qualitative investigation embedded within a 5-year Randomised Controlled Trial (RCT) examined the risks and benefits of Overdose Education and Naloxone Distribution (OEND) training models (brief or extended training) in various populations of people who use opioids in New York City. The qualitative experiences (obtained through semi-structured interviews) of 46 people who use opioids and who were each involved in the delivery of naloxone, during 56 separate overdose events that occurred throughout 2016-2018, were studied. Situational analysis and inductive content analysis of interview data focused upon overdose reversals in an attempt to provide understandings of the various adverse effects associated with naloxone from their perspective. These analyses were supplemented by data sessions within the research team during which the findings obtained from situational analysis and inductive content analysis were reviewed and complemented by deductive (clinical) appraisals of the various physical and psychological effects associated with the overdose reversals.

RESULTS

People who use opioids recognise three distinct and interconnected outcomes that may follow a successful opioid overdose reversal after intramuscular or intranasal administration of naloxone. These outcomes are here termed, (i) 'rage' (describing a wide range of angry, hostile and/or aggressive outbursts), (ii) 'withdrawal symptoms,' and (iii) 'not rage, not withdrawal' (i.e., a wide range of short-lived, 'harmless' conditions (such as temporary amnesia, mild emotional outbursts, or physical discomfort) that do not include rage or withdrawal symptoms).

CONCLUSION

Physical and psychological reactions to naloxone should not be understood exclusively as a consequence of acute, opioid-related, withdrawal symptoms. The three distinct and interconnected reversal outcomes identified in this study are considered from a harm reduction policy perspective and are further framed by concepts associated with 'mediated toxicity' (i.e., harm triggered by medicine). The overall conclusion is that harm reduction training programmes that are aligned to the policy and practice of take home naloxone may be strengthened by including awareness and training in how to best respond to 'rage' associated with overdose reversal following naloxone administration by people who use opioids and other laypersons.