Increasingly powerful opioid antagonists are not necessary

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.

Fact vs. fiction: naloxone in the treatment of opioid-induced respiratory depression in the current era of synthetic opioids

Opioid-induced respiratory depression (OIRD) deaths are ~80,000 a year in the US and are a major public health issue. Approximately 90% of fatal opioid-related deaths are due to synthetic opioids such as fentanyl, most of which is illicitly manufactured and distributed either on its own or as an adulterant to other drugs of abuse such as cocaine or methamphetamine. Other potent opioids such as nitazenes are also increasingly present in the illicit drug supply, and xylazine, a veterinary tranquilizer, is a prevalent additive to opioids and other drugs of abuse. Naloxone is the main treatment used to reverse OIRD and is available as nasal sprays, prefilled naloxone injection devices, and generic naloxone for injection. An overdose needs to be treated as soon as possible to avoid death, and synthetic opioids such as fentanyl are up to 50 times more potent than heroin, so the availability of new, higher-dose, 5-mg prefilled injection or 8-mg intranasal spray naloxone preparations are important additions for emergency treatment of OIRDs, especially by lay people in the community. Higher naloxone doses are expected to reverse a synthetic overdose more rapidly and the current formulations are ideal for use by untrained lay people in the community. There are potential concerns about severe withdrawal symptoms, or pulmonary edema from treatment with high-dose naloxone. However, from the perspective of first responders, the balance of risks would point to administration of naloxone at the dose required to combat the overdose where the risk of death is very high. The presence of xylazines as an adulterant complicates the treatment of OIRDs, as naloxone is probably ineffective, although it will reverse the respiratory depression due to the opioid. For these patients, hospitalization is particularly vital. Education about the benefits of naloxone remains important not only in informing people about how to treat emergency OIRDs but also how to obtain naloxone. A call to emergency services is also essential after administering naloxone because, although the patient may revive, they may overdose again later because of the short half-life of naloxone and the long-lasting potency of fentanyl and its analogs.

Comparison of Administration of 8-Milligram and 4-Milligram Intranasal Naloxone by Law Enforcement During Response to Suspected Opioid Overdose - New York, March 2022-August 2023

In 2021, an 8-mg intranasal naloxone product was approved by the Food and Drug Administration; however, no studies have examined outcomes among persons who receive the 8-mg naloxone product and those who receive the usual 4-mg product. During March 2022-August 2023, New York State Department of Health (NYSDOH) supplied some New York State Police (NYSP) troops with 8-mg intranasal naloxone; other troops continued to receive 4-mg intranasal naloxone to treat suspected opioid overdose. NYSP submitted detailed reports to NYSDOH when naloxone was administered. No significant differences were observed in survival, mean number of naloxone doses administered, prevalence of most postnaloxone signs and symptoms, postnaloxone anger or combativeness, or hospital transport refusal among 4-mg and 8-mg intranasal naloxone recipients; however, persons who received the 8-mg intranasal naloxone product had 2.51 times the risk for opioid withdrawal signs and symptoms, including vomiting, than did those who received the 4-mg intranasal naloxone product (95% CI = 1.51-4.18). This initial study suggests no benefits to law enforcement administration of higher-dose naloxone were identified; more research is needed to guide public health agencies in considering whether 8-mg intranasal naloxone confers additional benefits for community organizations.

Stronger, longer, better opioid antagonists? Nalmefene is NOT a naloxone replacement

The fatal overdose crisis claims nearly 200 lives daily in the United States (U.S). Evolutions in the illicit drug supply, such as the addition of sedative adulterants and a shift to synthetic opioids such as fentanyl, have driven increasing rates of both fatal and non-fatal overdose. Specifically, synthetic opioid usage of fentanyl was implicated in 68 % of the U.S. drug overdose deaths in 2022 alone. This has placed tremendous burden on communities, emergency medical services, and healthcare systems, and contributed to tragedy and grief both in the U.S. and worldwide. Despite the availability of effective opioid antagonist medications and standards of care, there has been increased interest in research and development of alternative opioid overdose reversal agents by the National Institutes of Health (NIH) in partnership with pharmaceutical manufacturers over the last decade. The U.S. Food and Drug Administration (FDA) recently approved nalmefene (Opvee) a mu-opioid receptor antagonist that boasts an extended half-life and stronger mu-receptor affinity compared to the standard of care use of naloxone for opioid reversal. In this article, we explore the medical need and ramifications of the introduction of longer-acting opioid antagonists in the current opioid overdose landscape. Existing data highlight the effectiveness of already available naloxone products as a safe and effective standard of care. These data support the notion that stronger, longer-acting agents may be unnecessary, and their existence may cause undue harm, such as more severe and/or prolonged withdrawal symptoms, lead to challenging patient interactions, and complicate the initiation of medications for opioid use disorder. More evidence is needed before healthcare professionals should implement the use of stronger, longer-acting opioid antagonists for reversing opioid overdose over evidence-based, cost-effective naloxone.

Intranasal Naloxone Repeat Dosing Strategies and Fentanyl Overdose: A Simulation-Based Randomized Clinical Trial

Importance

Questions have emerged as to whether standard intranasal naloxone dosing recommendations (ie, 1 dose with readministration every 2-3 minutes if needed) are adequate in the era of illicitly manufactured fentanyl and its derivatives (hereinafter, fentanyl).

Objective

To compare naloxone plasma concentrations between different intranasal naloxone repeat dosing strategies and to estimate their effect on fentanyl overdose.

Design, Setting, and Participants

This unblinded crossover randomized clinical trial was conducted with healthy participants in a clinical pharmacology unit (Spaulding Clinical Research, West Bend, Wisconsin) in March 2021. Inclusion criteria included age 18 to 55 years, nonsmoking status, and negative test results for the presence of alcohol or drugs of abuse. Data analysis was performed from October 2021 to May 2023.

Intervention

Naloxone administered as 1 dose (4 mg/0.1 mL) at 0, 2.5, 5, and 7.5 minutes (test), 2 doses at 0 and 2.5 minutes (test), and 1 dose at 0 and 2.5 minutes (reference).

Main Outcomes and Measures

The primary outcome was the first prespecified time with higher naloxone plasma concentration. The secondary outcome was estimated brain hypoxia time following simulated fentanyl overdoses using a physiologic pharmacokinetic-pharmacodynamic model. Naloxone concentrations were compared using paired tests at 3 prespecified times across the 3 groups, and simulation results were summarized using descriptive statistics.

Results

This study included 21 participants, and 18 (86%) completed the trial. The median participant age was 34 years (IQR, 27-50 years), and slightly more than half of participants were men (11 [52%]). Compared with 1 naloxone dose at 0 and 2.5 minutes, 1 dose at 0, 2.5, 5, and 7.5 minutes significantly increased naloxone plasma concentration at 10 minutes (7.95 vs 4.42 ng/mL; geometric mean ratio, 1.95 [1-sided 97.8% CI, 1.28-∞]), whereas 2 doses at 0 and 2.5 minutes significantly increased the plasma concentration at 4.5 minutes (2.24 vs 1.23 ng/mL; geometric mean ratio, 1.98 [1-sided 97.8% CI, 1.03-∞]). No drug-related serious adverse events were reported. The median brain hypoxia time after a simulated fentanyl 2.97-mg intravenous bolus was 4.5 minutes (IQR, 2.1-∞ minutes) with 1 naloxone dose at 0 and 2.5 minutes, 4.5 minutes (IQR, 2.1-∞ minutes) with 1 naloxone dose at 0, 2.5, 5, and 7.5 minutes, and 3.7 minutes (IQR, 1.5-∞ minutes) with 2 naloxone doses at 0 and 2.5 minutes.

Conclusions and Relevance

In this clinical trial with healthy participants, compared with 1 intranasal naloxone dose administered at 0 and 2.5 minutes, 1 dose at 0, 2.5, 5, and 7.5 minutes significantly increased naloxone plasma concentration at 10 minutes, whereas 2 doses at 0 and 2.5 minutes significantly increased naloxone plasma concentration at 4.5 minutes. Additional research is needed to determine optimal naloxone dosing in the community setting.

Trial Registration

ClinicalTrials.gov Identifier: NCT04764630.

The effect of untargeted naloxone distribution on opioid overdose outcomes

Opioid overdose has claimed the lives of over 340,000 Americans in the last decade. Over that same period, policymakers have taken steps to increase the availability of naloxone-an opioid antagonist used to rescue overdose victims-to people in the community. Previous studies, most of which have examined the effects of state laws designed to facilitate access to naloxone, have reached mixed conclusions about the effects of naloxone access on fatal and non-fatal overdoses. This paper exploits a unique policy experiment provided by two naloxone giveaways intended to increase naloxone possession among the general public in Pennsylvania to estimate the causal impact of naloxone distribution on fatal overdoses and opioid-related emergency department (ED) visits. Using a difference-in-differences design, I find evidence that opioid overdose deaths fell immediately following the first giveaway but increased following the second giveaway and discuss these apparently contradictory findings in the context of the changing composition of the opioid supply. I also find some evidence of a decline in opioid overdose-related ED visits following the giveaways. This study is the first to examine the effects of untargeted naloxone distribution and has implications for other novel, naloxone distribution efforts currently underway.

Bystander preference for naloxone products: a field experiment

BACKGROUND

Bystander administration of naloxone is a critical strategy to mitigate opioid overdose mortality. To ensure bystanders' willingness to carry and administer naloxone in response to a suspected overdose, it is critical to select products for community distribution with the highest likelihood of being utilized. This study examines bystanders' preference for and willingness to administer three naloxone products approved by the FDA for bystander use and identify product features driving preference.

METHODS

The population was a convenience sample of individuals who attended the Kentucky State Fair, August 18-28, 2022, in Louisville, Kentucky. Participants (n = 503) watched a standardized overdose education and naloxone training video, rated their willingness to administer each of three products (i.e., higher-dose nasal spray, lower-dose nasal spray, intramuscular injection), selected a product to take home, and rated factors affecting choice.

RESULTS

After training, 44.4% chose the higher-dose nasal spray, 30.1% chose the intramuscular injection, and 25.5% chose the lower-dose nasal spray. Factors most influencing choice on a 10-point Likert scale were ease of use (9 [7-10]), naloxone dose (8 [5-10]), and product familiarity (5 [5-9]).

CONCLUSIONS

Bystanders expressed high willingness to administer all studied formulations of naloxone products. Product choice preference varied as a function of product features. As the number and variety of available products continue to increase, continuous evaluation of formulation acceptability, in addition to including individuals with lived experience who are receiving and administering overdose reversal agents, is critical to support adoption and save lives.

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.

I Don't Believe a Person Has to Die When Trying to Get High: Overdose Prevention and Response Strategies in Rural Illinois

BACKGROUND

Overdose is a leading cause of morbidity and mortality among people who inject drugs. Illicitly manufactured fentanyl is now a major driver of opioid overdose deaths.

METHODS

Semi-structured interviews were conducted with 23 participants (19 persons who inject drugs and 4 service providers) from rural southern Illinois. Data were analyzed using constant comparison and theoretical sampling methods.

RESULTS

Participants were concerned about the growing presence of fentanyl in both opioids and stimulants, and many disclosed overdose experiences. Strategies participants reported using to lower overdose risk included purchasing drugs from trusted sellers and modifying drug use practices by partially injecting and/or changing the route of transmission. Approximately half of persons who inject drugs sampled had heard of fentanyl test strips, however fentanyl test strip use was low. To reverse overdoses, participants reported using cold water baths. Use of naloxone to reverse overdose was low. Barriers to naloxone access and use included fear of arrest and opioid withdrawal.

CONCLUSIONS

People who inject drugs understood fentanyl to be a potential contaminant in their drug supply and actively engaged in harm reduction techniques to try to prevent overdose. Interventions to increase harm reduction education and information about and access to fentanyl test strips and naloxone would be beneficial.

Naloxone administration by law enforcement officers in New York State (2015-2020)

BACKGROUND

The COVID-19 pandemic has amplified the need for wide deployment of effective harm reduction strategies in preventing opioid overdose mortality. Placing naloxone in the hands of key responders, including law enforcement officers who are often first on the scene of a suspected overdose, is one such strategy. New York State (NYS) was one of the first states to implement a statewide law enforcement naloxone administration program. This article provides an overview of the law enforcement administration of naloxone in NYS between 2015 and 2020 and highlights key characteristics of over 9000 opioid overdose reversal events.

METHODS

Data in naloxone usage report forms completed by police officers were compiled and analyzed. Data included 9133 naloxone administration reports by 5835 unique officers located in 60 counties across NYS. Descriptive statistics were used to examine attributes of the aided individuals, including differences between fatal and non-fatal incidents. Additional descriptive analyses were conducted for incidents in which law enforcement officers arrived first at the scene of suspected overdose. Comparisons were made to examine year-over-year trends in administration as naloxone formulations were changed. Quantitative analysis was supplemented by content analysis of officers' notes (n = 2192).

RESULTS

In 85.9% of cases, law enforcement officers arrived at the scene of a suspected overdose prior to emergency medical services (EMS) personnel. These officers assessed the likelihood of an opioid overdose having occurred based on the aided person's breathing status and other information obtained on the scene. They administered an average of 2 doses of naloxone to aided individuals. In 36.8% of cases, they reported additional administration of naloxone by other responders including EMS, fire departments, and laypersons. Data indicated the aided survived the suspected overdose in 87.4% of cases.

CONCLUSIONS

With appropriate training, law enforcement personnel were able to recognize opioid overdoses and prevent fatalities by administering naloxone and carrying out time-sensitive medical interventions. These officers provided life-saving services to aided individuals alongside other responders including EMS, fire departments, and bystanders. Further expansion of law enforcement naloxone administration nationally and internationally could help decrease opioid overdose mortality.

Patient perceptions of higher-dose naloxone nasal spray for opioid overdose

BACKGROUND

Higher-dose formulations of naloxone were recently approved by the FDA for the treatment of opioid overdose. These products were developed based on projected saturation of high-potency fentanyl analogues in the illicit marketplace although the evidence base for their necessity is still under scrutiny. Concern has been raised that unintended reductions in patient acceptance of naloxone may occur due to increased precipitated withdrawal risk associated with higher naloxone doses. A well-founded and time-sensitive call for representation of people who use drugs in this decision-making process has been made. This study provides the first data on patient perceptions of higher-dose formulations to inform this scientific debate and distribution efforts.

METHODS

Patients (N=1152) entering treatment for opioid use disorder at one of 49 addiction treatment facilities located across the United States completed a preference assessment of naloxone nasal spray formulations. Patients selected a formulation preference across three scenarios (administration for self, administration to others, community responder administration).

RESULTS

A majority of respondents that had been administered naloxone previously reported that their most recent overdose reversal included two or more naloxone administrations (59.9%). Most respondents either had no preference (48.4%) or preferred a higher-dose formulation (35.9%) if personally experiencing an overdose. Similar preference distributions were observed for administration to others and by community responders. Relative to standard-dose preference, respondents preferring higher-dose formulations had a greater odds of recent suspected fentanyl exposure.

CONCLUSIONS

These data inform patients, advocates, and policy-makers considering distribution and utilization of naloxone formulations by reporting perspectives of patients with opioid use and overdose experience. Limited evidence for widespread avoidance of higher-dose formulations was found. As real-world evidence of acceptability and effectiveness emerges, either supporting or refuting the widespread need for higher-dose naloxone formulations, it is the responsibility of the scientific and public health community to be responsive to those data.

Treatment of opioid overdose: current approaches and recent advances

BACKGROUND

The USA has recently entered the third decade of the opioid epidemic. Opioid overdose deaths reached a new record of over 74,000 in a 12-month period ending April 2021. Naloxone is the primary opioid overdose reversal agent, but concern has been raised that naloxone is not efficacious against the pervasive illicit high potency opioids (i.e., fentanyl and fentanyl analogs).

METHODS

This narrative review provides a brief overview of naloxone, including its history and pharmacology, and the evidence regarding naloxone efficacy against fentanyl and fentanyl analogs. We also highlight current advances in overdose treatments and technologies that have been tested in humans.

RESULTS AND CONCLUSIONS

The argument that naloxone is not efficacious against fentanyl and fentanyl analogs rests on case studies, retrospective analyses of community outbreaks, pharmacokinetics, and pharmacodynamics. No well-controlled studies have been conducted to test this argument, and the current literature provides limited evidence to suggest that naloxone is ineffective against fentanyl or fentanyl analog overdose. Rather a central concern for treating fentanyl/fentanyl analog overdose is the rapidity of overdose onset and the narrow window for treatment. It is also difficult to determine if other non-opioid substances are contributing to a drug overdose, for which naloxone is not an effective treatment. Alternative pharmacological approaches that are currently being studied in humans include other opioid receptor antagonists (e.g., nalmefene), respiratory stimulants, and buprenorphine. None of these approaches target polysubstance overdose and only one novel approach (a wearable naloxone delivery device) would address the narrow treatment window.

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.