Naloxone dosage for opioid reversal: current evidence and clinical implications

A humanized monoclonal antibody attenuates fentanyl self-administration and reverses and prevents fentanyl-induced ventilatory depression in rhesus monkeys

Medications for opioid use disorder (OUD) and overdose have been available for decades, yet nearly 70% of fatal drug overdoses in the United States are attributed to the opioid receptor agonist fentanyl and its analogs. There is a pressing need for more and better medications that reduce fentanyl use and prevent overdose. A humanized (h) monoclonal antibody (mAb) targeting fentanyl, hHY6-F9, was tested for attenuating intravenous fentanyl self-administration and reversing and preventing fentanyl-induced ventilatory depression in rhesus monkeys. A single administration of hHY6-F9 significantly decreased fentanyl, but not heroin or cocaine, self-administration. In some monkeys, fentanyl self-administration remained decreased for ~ 2 weeks. hHY6-F9 was as effective as 32 µg/kg naloxone in reversing fentanyl-induced ventilatory depression, with a single administration protecting against fentanyl-induced ventilatory depression for 2-3 weeks. Moreover, pharmacokinetic analyses indicate that hHY6-F9 continued to sequester fentanyl in the serum for 2 weeks. This study demonstrates that hHY6-F9 selectively attenuates the positive reinforcing and ventilatory depressant effects of fentanyl, indicating its possible utility for preventing relapse and overdose.

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.

An interrupted time series analysis of fentanyl, naloxone, and opioid-involved deaths in five counties in Eastern Missouri

INTRODUCTION

Rates of opioid overdose deaths (OOD) have increased since the introduction of illicitly manufactured fentanyl in the U.S. drug supply. Though community-based naloxone distribution efforts have been found to effectively reduce OOD, no studies to date have examined their effects during the fentanyl era, nor in the epicenter of a state's overdose crisis. Thus, the current study assessed the impacts of both fentanyl and of subsequent grant-funded community-based naloxone distribution on OOD across Missouri's St. Louis region.

METHODS

Medical examiner data includes individuals who died within one of the five study counties (St. Louis City, St. Louis County, and Franklin, Jefferson, St. Charles counties [combined as "Collar Counties"]) between 2011 and 2022 due to an opioid overdose (N = 6,799). Naloxone distribution date and location data came from Missouri's university-based naloxone distribution team. We conducted a controlled interrupted time series using an autoregressive model via proc ARIMA to examine changes over time in the rate of OOD associated with the introduction of fentanyl (defined to be present in 25% of opioid overdose deaths; June 2015) and the start of naloxone distribution for each location (August 2017, October 2017, and January 2018, respectively).

RESULTS

The introduction of fentanyl into the drug supply of St. Louis City was associated with an increased rate of OOD over time (p < .001). Naloxone distribution in the City was associated with an immediate decrease in OOD (p < .001) followed by a slowed increase in OOD (p < .001). These findings were not replicated in St. Louis County nor the Collar Counties.

CONCLUSIONS

The effects of fentanyl and naloxone on OOD varied by region in Eastern Missouri. Specifically, fentanyl and naloxone effects were only found in a high-need urban area with existing harm reduction and street outreach programs, but not in surrounding suburban or rural areas. State-level naloxone distribution decision-makers should prioritize funding harm reduction services in both urban and non-urban settings to help increase targeted naloxone distribution to those actively using drugs. Additionally, interventions tailored for people who engage in solitary drug use - such as safe consumption spaces and overdose detection technologies - should receive increased investment and implementation, particularly in rural areas where harm reduction infrastructure is more scarce.

Development and preclinical testing of a naloxone prodrug depot for extended protection against opioid overdose

The opioid crisis, driven by synthetic opioids like fentanyl, demands innovative solutions. The opioid antidote naloxone has a short action ( ~ 1 hour), requiring repeated doses. To address this, we present a new and simple naloxone prodrug delivery system repurposing a hydrophilic derivative of acoramidis, a potent transthyretin ligand. When the fully soluble prodrug solution is administered subcutaneously, the prodrug forms a zwitterionic depot at physiological pH, enabling extended naloxone release. This non-polymeric depot-forming approach is rare and employs carboxylesterase 2 for selective bioactivation, ensuring controlled drug release. In male rats and cynomolgus monkeys, a single subcutaneous dose provides steady naloxone release over several days, reducing blood-brain barrier diffusion, withdrawal symptoms, and CNS toxicity. Preclinical studies demonstrated efficacy in rat overdose models and achieved monkey naloxone levels matching effective human therapeutic levels. Although monkey efficacy was not assessed, combined rat efficacy and monkey pharmacokinetics suggest strong potential for successful human translation.

Blood pressure response to extended-release naltrexone in heroin and prescription opioid users and its implications for cardiovascular morbidity

BACKGROUND

Consuming opioid agonists is a risk factor for cardiovascular disease particularly in intravenous heroin users. The monthly injectable extended-release opioid antagonist, naltrexone (XR-NTX) is an effective treatment for opioid use disorder. The impact of opioid receptor blockade through XR-NTX on blood pressure, a critical risk factor for cardiovascular morbidity, has not yet been characterized.

METHODS

The study evaluated the change in blood pressure during XR-NTX treatment among 14 patients who predominately used intravenous heroin and 24 patients who used prescription oral opioids, all with opioid use disorder. Blood pressure was measured in each patient immediately before the first XR-NTX injection and ∼two weeks after the first injection. The change in diastolic and systolic pressure was compared between the heroin users and the prescription opioids users using analysis of variance.

RESULTS

XR-NTX treatment was associated with significant decreases in diastolic blood pressure in the heroin group, but not in the prescription opioids group. Systolic blood pressure values in the heroin users showed a decline at trend level only.

CONCLUSIONS

Further research is warranted to replicate our findings and to determine whether XR-NTX effect is relatively specific to blood pressure or generalizes to other components of metabolic syndrome. Distinguishing between heroin and prescription opioid users could shed light on the unique clinical and pharmacological profiles of opioid drugs, particularly regarding their cardiovascular safety. This information can be useful in developing personalized therapeutic strategies based on the route of opioid administration.

Naloxone administration and survival in overdoses involving opioids and stimulants: An analysis of law enforcement data from 63 Pennsylvania counties

BACKGROUND

In consideration of rising opioid-stimulant deaths in the United States, this study explored rates of naloxone administration and survival in suspected opioid overdoses with, versus without, stimulants co-involved.

METHODS

The study analyzed 26,635 suspected opioid-involved overdoses recorded by law enforcement/first-responders in the Pennsylvania Overdose Information Network in 63 Pennsylvania counties, January 2018-July 2024. All measures, including suspected drug involvement, were based on first-responder assessment/report. Relative frequencies and chi-square tests were first used to compare suspected opioid overdoses with, versus without, stimulants (cocaine or methamphetamine) co-involved. Next, mediation analyses tested naloxone administration as a mediator in the association between stimulant co-involvement (in opioid overdoses) and survival.

RESULTS

Naloxone was reportedly administered in 72.2 % of the suspected opioid-no-cocaine overdoses, compared to 55.1 % of the opioid-cocaine-involved overdoses, and 72.1 % of the opioid-no-methamphetamine overdoses vs. 52.4 % of the opioid-methamphetamine-involved overdoses. With respect to survival rates, 18.0 % of the suspected opioid-no-cocaine overdoses ended in death, compared to 41.3 % of the opioid-cocaine overdoses; 18.1 % of the opioid-no-methamphetamine overdoses ended in death, versus 42.9 % of the opioid-methamphetamine overdoses. In mediation analyses (adjusted for demographics, county, year, and other drug co-involvement), naloxone administration mediated 38.7 % (95 % Confidence Interval [CI], 31.3-46.0 %) of the association between suspected cocaine co-involvement and survival and 39.2 % (95 % CI, 31.3-47.1 %) of the association between suspected methamphetamine co-involvement and survival.

CONCLUSIONS

Among suspected opioid overdoses recorded in the Pennsylvania Overdose Information Network, stimulant co-involvement was associated with lower naloxone administration and higher fatality, with naloxone partially mediating the association between stimulant co-involvement and death.

Patent Review of Novel Biologics Targeting Opioid Use Disorder (2018-2024)

Drug overdose deaths in 2023 in the United States exceeded 107,000, with 80,000 of these deaths attributed to opioids alone. The emergence of synthetic opioids such as fentanyl and its analogues have worsened the opioid overdose epidemic. A novel approach to treat opioid overdose and opioid use disorder (OUD) has been the introduction of biologics, which include monoclonal antibodies that bind to circulating opioids, preventing them from reaching the central nervous system, or peptides that have antinociceptive effects but lack the abuse liability of synthetic opioids. A challenge in the treatment of opioid overdose has been renarcotization, where an overdose patient revived with naloxone can re-enter an overdose state from residual opioid in the body. Biologics such as vaccines and monoclonal antibodies are excellent strategies that have been demonstrated to prevent renarcotization. In this review, we retrieved and discussed patents filed in the past six (6) years that focus on novel biologics reported as treatments for opioid overdose and OUD. We also provide a perspective on the use of biologics as therapeutics for OUD and opioid overdose.

Prediction of naloxone dose in opioids toxicity based on machine learning techniques (artificial intelligence)

BACKGROUND

Treatment management for opioid poisoning is critical and, at the same time, requires specialized knowledge and skills. This study was designed to develop and evaluate machine learning algorithms for predicting the maintenance dose and duration of hospital stay in opioid poisoning, in order to facilitate appropriate clinical decision-making.

METHOD AND RESULTS

This study used artificial intelligence technology to predict the maintenance dose and duration of administration by selecting clinical and paraclinical features that were selected by Pearson correlation (filter method) (Stage 1) and then the (wrapper method) Recursive Feature Elimination Cross-Validated (RFECV) (Stage2). The duration of administration was divided into two categories: A (which includes a duration of less than or equal to 24 h of infusion) and B (more than 24 h of naloxone infusion). XGBoost algorithm model with an accuracy rate of 91.04%, a prediction rate of 91.34%, and a sensitivity rate of 91.04% and area under the Curve (AUC) 0.97 was best model for classification patients. Also, the best maintenance dose of naloxone was obtained with XGBoost algorithm with R2 = 0.678. Based on the selected algorithm, the most important features for classifying patients for the duration of treatment were bicarbonate, respiration rate, physical sign, The partial pressure of carbon dioxide (PCO2), diastolic blood pressure, pulse rate, naloxone bolus dose, Blood Creatinine(Cr), Body temperature (T). The most important characteristics for determining the maintenance dose of naloxone were physical signs, bolus dose of 4.5 mg/kg, Glasgow Coma Scale (GCS), Creatine Phosphokinase (CPK) and intensive care unit (ICU) add.

CONCLUSION

A predictive model can significantly enhance the decision-making and clinical care provided by emergency physicians in hospitals and medical settings. XGBoost was found to be the superior model.

Hypoxic effects of heroin and fentanyl and their basic physiological mechanisms

Respiratory depression that diminishes oxygen delivery to the brain is the most dangerous effect of opioid drugs. Although plethysmography is a valuable tool to examine drug-induced changes in respiration, the primary cause of brain abnormalities induced by opioids is the global decrease in brain oxygen levels. The primary goal of this review is to provide an overview and discussion on fluctuations in brain oxygen levels induced by opioids, with a focus on heroin and fentanyl. To evaluate fluctuations in brain oxygen levels, we used oxygen sensors coupled with high-speed amperometry in awake, freely moving rats. First, we provide an overview of brain oxygen responses induced by natural physiological stimuli and discuss the mechanisms regulating oxygen entry into brain tissue. Then, we present data on brain oxygen responses induced by heroin and fentanyl and review their underlying mechanisms. These data allowed us to compare the effects of these drugs on brain oxygen regarding their latency, potency, time-dependency, and potential lethality at high doses as well as their relationships with peripheral oxygen responses. We also discuss data on the effects of naloxone on brain oxygen responses induced by heroin and fentanyl in the paradigms of both the pretreatment and treatment, when naloxone is administered at different times after the primary opioid drug. Although most data discussed were obtained in rats, they may have clinical relevance for understanding the mechanisms underlying the physiological effects of opioids and developing rational treatment strategies to decrease acute lethality and long-term health complications of opioid misuse.

Naloxone Administration and Survival in Overdoses Involving Opioids and Stimulants: An Analysis of Law Enforcement Data from 63 Pennsylvania Counties

Background

In consideration of rising opioid-stimulant deaths in the United States, this study explored rates of naloxone administration and survival in suspected opioid overdoses with, versus without, stimulants co-involved.

Methods

The study analyzed 26,635 suspected opioid-involved overdoses recorded by law enforcement/first-responders in the Pennsylvania Overdose Information Network in 63 Pennsylvania counties, January 2018-July 2024. All measures, including suspected drug involvement, were based on first-responder assessment/report. Relative frequencies and chi-square tests were first used to compare suspected opioid overdoses with, versus without, stimulants (cocaine or methamphetamine) co-involved. Next, mediation analyses tested naloxone administration as a mediator in the association between stimulant co-involvement (in opioid overdoses) and survival.

Results

Naloxone was reportedly administered in 72.2% of the suspected opioid-no-cocaine overdoses, compared to 55.1% of the opioid-cocaine-involved overdoses, and 72.1% of the opioid-no-methamphetamine overdoses vs. 52.4% of the opioid-methamphetamine-involved overdoses. With respect to survival rates, 18.0% of the suspected opioid-no-cocaine overdoses ended in death, compared to 41.3% of the opioid-cocaine overdoses; 18.1% of the opioid-no-methamphetamine overdoses ended in death, versus 42.9% of the opioid-methamphetamine overdoses. In mediation analyses (adjusted for demographics, county, year, and other drug co-involvement), naloxone administration mediated 38.7% (95% Confidence Interval [CI], 31.3%-46.0%) of the association between suspected cocaine co-involvement and survival and 39.2% (95% CI, 31.3%-47.1%) of the association between suspected methamphetamine co-involvement and survival.

Conclusions

Among suspected opioid overdoses recorded in the Pennsylvania Overdose Information Network, stimulant co-involvement was associated with lower naloxone administration and higher fatality, with naloxone partially mediating the association between stimulant co-involvement and death.

Consensus Statement on Pain Management for Pregnant Patients with Opioid-Use Disorder from the Society for Obstetric Anesthesia and Perinatology, Society for Maternal-Fetal Medicine, and American Society of Regional Anesthesia and Pain Medicine

Pain management in pregnant and postpartum people with an opioid-use disorder (OUD) requires a balance between risks associated with opioid tolerance, including withdrawal or return to opioid use, considerations around social needs of the maternal-infant dyad, and the provision of adequate pain relief for the birth episode that is often characterized as the worst pain a person will experience in their lifetime. This multidisciplinary consensus statement between the Society for Obstetric Anesthesia and Perinatology (SOAP), Society for Maternal-Fetal Medicine (SMFM), and American Society of Regional Anesthesia and Pain Medicine (ASRA) provides a framework for pain management in obstetric patients with OUD. The purpose of this consensus statement is to provide practical and evidence-based recommendations and is targeted to health care providers in obstetrics and anesthesiology. The statement is focused on prenatal optimization of pain management, labor analgesia, and postvaginal delivery pain management, and postcesarean delivery pain management. Topics include a discussion of nonpharmacologic and pharmacologic options for pain management, medication management for OUD (eg, buprenorphine, methadone), considerations regarding urine drug testing, and other social aspects of care for maternal-infant dyads, as well as a review of current practices. The authors provide evidence-based recommendations to optimize pain management while reducing risks and complications associated with OUD in the peripartum period. Ultimately, this multidisciplinary consensus statement provides practical and concise clinical guidance to optimize pain management for people with OUD in the context of pregnancy to improve maternal and perinatal outcomes.

A brainstem circuit amplifies aversion

Dynamic gain control of aversive signals enables adaptive behavioral responses. Although the role of amygdalar circuits in aversive processing is well established, the neural pathway for amplifying aversion remains elusive. Here, we show that the brainstem circuit linking the interpeduncular nucleus (IPN) with the nucleus incertus (NI) amplifies aversion and promotes avoidant behaviors. IPN GABA neurons are activated by aversive stimuli and their predicting cues, with their response intensity closely tracking aversive values. Activating these neurons does not trigger aversive behavior on its own but rather amplifies responses to aversive stimuli, whereas their ablation or inhibition suppresses such responses. Detailed circuit dissection revealed anatomically distinct subgroups within the IPN GABA neuron population, highlighting the NI-projecting subgroup as the modulator of aversiveness related to fear and opioid withdrawal. These findings unveil the IPN-NI circuit as an aversion amplifier and suggest potential targets for interventions against affective disorders and opioid relapse.

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.

An autonomous implantable device for the prevention of death from opioid overdose

Opioid overdose accounts for nearly 75,000 deaths per year in the United States, now a leading cause of mortality among young people aged 18 to 45 years. At overdose levels, opioid-induced respiratory depression becomes fatal without the administration of naloxone within minutes. Currently, overdose survival relies on bystander intervention, requiring a nearby person to find the overdosed individual and have immediate access to naloxone to administer. To circumvent the bystander requirement, we developed the Naloximeter: a class of life-saving implantable devices that autonomously detect and treat overdose while simultaneously contacting first responders. We present three Naloximeter platforms, for fundamental research and clinical translation, all equipped with optical sensors, drug delivery mechanisms, and a supporting ecosystem of technology to counteract opioid-induced respiratory depression. In small and large animal studies, the Naloximeter rescues from otherwise fatal opioid overdose within minutes. This work introduces life-changing, clinically translatable technologies that can broadly benefit a susceptible population recovering from opioid use disorder.

An implantable system for opioid safety

Naloxone can effectively rescue victims from opioid overdose, but less than 5% survive due to delayed or absent first responder intervention. Current overdose reversal systems face key limitations, including low user adherence, false positive detection, and slow antidote delivery. Here, we describe a subcutaneously implanted robotic first responder to overcome these challenges. This implantable system for opioid safety continuously monitors vital signs, detecting opioid overdose through an algorithm analyzing the interplay of cardiorespiratory responses. To address battery concerns with continuous monitoring and multi-sensing modality, an adaptive algorithm dynamically adjusts sensor resolution, reducing the need for frequent charging. Furthermore, the implant includes an ultra-rapid naloxone delivery pump, delivering the 10-mg antidote within 10 s. In animal trials, the robotic first responder successfully revived 96% of overdosed pigs (n = 25) within 3.2 min, showcasing its potential to dramatically improve survival rates and combat the opioid epidemic.

In vitro and in vivo study of butyrylfentanyl and 4-fluorobutyrylfentanyl in female and male mice: Role of the CRF1 receptor in cardiorespiratory impairment

BACKGROUND AND PURPOSE

Fentanyl analogues have been implicated in many cases of intoxication and death with overdose worldwide. The aim of this study is to investigate the pharmaco-toxicology of two fentanyl analogues: butyrylfentanyl (BUF) and 4-fluorobutyrylfentanyl (4F-BUF).

EXPERIMENTAL APPROACH

In vitro, we measured agonist opioid receptor efficacy, potency, and selectivity and ability to promote interaction of the μ receptor with G protein and β-arrestin 2. In vivo, we evaluated thermal antinociception, stimulated motor activity and cardiorespiratory changes in female and male CD-1 mice injected with BUF or 4F-BUF (0.1-6 mg·kg-1). Opioid receptor specificity was investigated using naloxone (6 mg·kg-1). We investigated the possible role of stress in increasing cardiorespiratory toxicity using the corticotropin-releasing factor 1 (CRF1) antagonist antalarmin (10 mg·kg-1).

KEY RESULTS

Agonists displayed the following rank of potency at μ receptors: fentanyl > 4F-BUF > BUF. Fentanyl and BUF behaved as partial agonists for the β-arrestin 2 pathway, whereas 4F-BUF did not promote β-arrestin 2 recruitment. In vivo, we revealed sex differences in motor and cardiorespiratory impairments but not antinociception induced by BUF and 4F-BUF. Antalarmin alone was effective in blocking respiratory impairment induced by BUF in both sexes but not 4F-BUF. The combination of naloxone and antalarmin significantly enhanced naloxone reversal of the cardiorespiratory impairments induced by BUF and 4F-BUF in mice.

CONCLUSION AND IMPLICATIONS

In this study, we have uncovered a novel mechanism by which synthetic opioids induce respiratory depression, shedding new light on the role of CRF1 receptors in cardiorespiratory impairments by μ agonists.

Take-home naloxone in multicentre emergency settings: the TIME feasibility cluster RCT

Background

Opioids kill more people than any other drug. Naloxone is an opioid antagonist which can be distributed in take-home 'kits' for peer administration (take-home naloxone).

Aim

To determine the feasibility of carrying out a definitive randomised controlled trial of take-home naloxone in emergency settings.

Design

We used Welsh routine data (2015-21) to test the feasibility of developing a discriminant function to identify people at high risk of fatal opioid overdose. We carried out a cluster randomised controlled trial and qualitative study to examine experiences of service users and providers. We assessed feasibility of intervention and trial methods against predetermined progression criteria related to: site sign-up, staff trained, identification of eligible patients, proportion given kits, identification of people who died of opioid poisoning, data linkage and retrieval of outcomes.

Setting

This study was carried out in the emergency environment; sites comprised an emergency department and associated ambulance service catchment area.

Participants

At intervention sites, we invited emergency department clinicians and paramedics to participate. We recruited adult patients who arrived at the emergency department or were attended to by ambulance paramedics for a problem related to opioid use with capacity to consent to receiving the take-home naloxone and related training.

Interventions

Usual care comprised basic life support plus naloxone by paramedics or emergency department staff. The take-home naloxone intervention was offered in addition to usual care, with guidance for recipients on basic life support, the importance of calling the emergency services, duration of effect, safety and legality of naloxone administration.

Discriminant function

With low numbers of opioid-related deaths (1105/3,227,396) and a high proportion having no contact with health services in the year before death, the predictive link between death and opioid-related healthcare events was weak. Logistic regression models indicated we would need to monitor one-third of the population to capture 75% of the decedents from opioid overdose in 1-year follow-up.

Randomised controlled trial

Four sites participated in the trial and 299 of 687 (44%) eligible clinical staff were trained. Sixty take-home naloxone kits were supplied to patients during 1-year recruitment. Eligible patients were not offered take-home naloxone kits 164 times: 'forgot' (n = 136); 'too busy' (n = 15); suspected intentional overdose (n = 3).

Qualitative interviews

Service users had high levels of knowledge about take-home naloxone. They were supportive of the intervention but noted concerns about opioid withdrawal and resistance to attending hospital for an overdose. Service providers were positive about the intervention but reported barriers including difficulty with consenting and training high-risk opioid users.

Health economics

We were able to calculate costs to train staff at three sites (£40 per AS and £17 in Site 1 ED). No adverse events were reported. Progression criteria were not met - fewer than 50% of eligible staff were trained, fewer than 50% of eligible patients received the intervention and outcomes were not retrieved within reasonable timescales.

Future work

The take-home naloxone intervention needs to be developed and evaluated in emergency care settings, with appropriate methods.

Limitations

The Take-home naloxone Intervention Multicentre Emergency setting study was interrupted by coronavirus disease.

Conclusions

This study did not meet progression criteria for intervention or trial methods feasibility, so outcomes were not followed up and a fully powered trial is not planned.

Trial registration

This trial is registered as ISRCTN13232859.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 16/91/04) and is published in full in Health Technology Assessment; Vol. 28, No. 74. See the NIHR Funding and Awards website for further award information.

Effectiveness of intramuscular naloxone 1,600 μg in addition to titrated intravenous naloxone 100 μg for opioid poisoning: a randomised controlled trial

INTRODUCTION

Naloxone is an effective antidote, but its short half-life means repeated doses, and infusions are often required. We investigated the effectiveness of adding intramuscular naloxone to titrated intravenous naloxone in opioid overdose in preventing recurrence of respiratory depression.

METHODS

This double-blinded randomised placebo-controlled trial was conducted in patients with suspected opioid poisoning and respiratory depression (respiratory rate <10 breaths/min or oxygen saturation <93%). Patients were randomised to receive either intramuscular naloxone 1,600 µg or saline placebo. All patients received titrated intravenous naloxone 100 µg and were managed on an opioid poisoning care pathway. The primary outcome was recurrence of respiratory depression within 4 h. Secondary outcomes were the proportion receiving naloxone infusions, number of naloxone boluses administered, reversal of respiratory depression at 10 min, and precipitation of opioid withdrawal (any symptom).

RESULTS

Recurrence of respiratory depression within 4 h was less common in 28/69 (41%) patients receiving intramuscular naloxone versus 48/67 (72%) patients receiving placebo (difference 31%, 95% CI: 13-46%; P < 0.001). Fewer naloxone infusions (5/69; 7% versus 25/67; 37%, difference 30%, 95% CI: 15 to 55%; P < 0.001) and fewer naloxone doses were administered (median 2, IQR: 1 to 5, versus median 5, IQR: 2 to 8; P = 0.001) in the intramuscular group. Reversal of respiratory depression at 10 min was similar between groups (51/69; 74% intramuscular naloxone versus 47/67; 70% placebo; P = 0.703). Opioid withdrawal occurred in 35/69 (51%) given intramuscular naloxone compared to 28/67 (42%) in the placebo group (difference 9%; 95% CI: -8 to 27%; P = 0.308).

DISCUSSION

The favourable pharmacokinetics of intramuscular naloxone, particularly its longer duration of activity, likely explains the improved effectiveness with lower recurrence of respiratory depression.

CONCLUSION

The addition of intramuscular naloxone 1,600 µg to titrated intravenous naloxone prolonged effective reversal of respiratory depression, with fewer naloxone doses and infusions given, and no significant difference in patients developing withdrawal.

Potentially Life-Threatening Interaction between Opioids and Intrathecal Baclofen in Individuals with a Childhood-Onset Neurological Disorder: A Case Series and Review of the Literature

BACKGROUND

Spasticity and dystonia are movement impairments that can occur in childhood-onset neurological disorders. Severely affected individuals can be treated with intrathecal baclofen (ITB). Concomitant use of ITB and opioids has been associated with central nervous system (CNS) depression. This study aims to describe the clinical management of this interaction, based on a case series and review of literature.

METHODS

Four individuals with childhood-onset CNS disorders (age 8-24) and CNS-depressant overdose symptoms after the concomitant use of ITB and opioids are described. The Drug Interaction Probability Scale (DIPS) was calculated to assess the cause-relationship (doubtful <2, possible 2-4, probable 5-8, and highly probable >8) of the potential drug-drug interaction. A literature review of similar previously reported cases and the possible pharmacological mechanisms of opioid-baclofen interaction is provided.

RESULTS

After ITB and opioid co-administration, three out of four patients had decreased consciousness, and three developed respiratory depression. DIPS scores indicated a possible cause-relationship in one patient (DIPS: 4) and a probable cause-relationship in the others (DIPS: 6, 6, and 8). Discontinuation or adjusting ITB or opioid dosages resulted in clinical recovery. All patients recovered completely. In the literature, two articles describing nine unique cases were found.

CONCLUSION

Although the opioid-ITB interaction is incompletely understood, concomitant use may enhance the risk of symptoms of CNS-depressant overdose, which are potentially life-threatening. If concomitant use is desirable, we strongly recommend to closely monitor these patients to detect interaction symptoms early. Awareness and monitoring of the potential opioid-ITB interaction is essential to reduce the risk of severe complications.

Comparison of the μ-Opioid Receptor Antagonists Methocinnamox and Naloxone to Reverse and Prevent the Ventilatory Depressant Effects of Fentanyl, Carfentanil, 3-Methylfentanyl, and Heroin in Male Rats

The number of opioid overdose deaths has increased significantly over the past decade. The life-threatening effect of opioids is hypoventilation, which can be reversed by the μ-opioid receptor (MOR) antagonist naloxone; however, because of the very short duration of action of naloxone, reemergence of MOR agonist-induced hypoventilation can occur, requiring additional doses of naloxone. The MOR antagonist methocinnamox (MCAM) antagonizes hypoventilation by the nonmorphinan fentanyl and the morphinan heroin in laboratory animals with an unusually long duration of action. Whole-body plethysmography was used to compare the potency and effectiveness of MCAM and naloxone for preventing and reversing hypoventilation by fentanyl, heroin, and the ultrapotent and longer-acting fentanyl analogs carfentanil and 3-methylfentanyl in male rats breathing normal air. Sessions comprised a 45-minute habituation period followed by intravenous administration of saline or an acute dose of MOR agonist. The rank order of potency to decrease ventilation was 3-methylfentanyl > carfentanil > fentanyl > heroin. MCAM (0.0001-0.1 mg/kg) and naloxone (0.0001-0.01 mg/kg) dose dependently reversed hypoventilation by 3-methylfentanyl (0.01 mg/kg), carfentanil (0.01 mg/kg), fentanyl (0.1 mg/kg), or heroin (3.2 mg/kg). For prevention studies, MCAM, naloxone, or vehicle was administered intravenously 22, 46, or 70 hours prior to a MOR agonist. When administered 22 hours earlier, MCAM (0.1-1.0 mg/kg) but not naloxone (1.0 mg/kg) prevented hypoventilation by each MOR agonist. This study demonstrates the effectiveness of MCAM at reversing and preventing hypoventilation by MOR agonists including ultrapotent fentanyl analogs that have a long duration of action. SIGNIFICANCE STATEMENT: The number of opioid overdose deaths increased over the past decade despite the availability of antagonists that can prevent and reverse the effects of opioids. This study demonstrates the effectiveness and long duration of action of the μ-opioid receptor (MOR) antagonist methocinnamox (MCAM) for reversing and preventing hypoventilation by MOR agonists including ultrapotent fentanyl analogs. These results provide support for the notion that MCAM has the potential to positively impact the ongoing opioid crisis by reversing and preventing opioid overdose.

Structure-Activity Relationships of the Fentanyl Scaffold: Identification of Antagonists as Potential Opioid Overdose Reversal Agents

Opioid-related overdoses account for almost half of all drug overdose deaths in the United States and cause more preventable deaths every year than car crashes. Fentanyl, a highly potent mu opioid receptor (MOR) agonist and its analogues (fentalogues) are increasingly found in illicit drug samples, both where the primary drug of abuse is an opioid and where it is not. The prevalence of fentalogues in the illicit drug market is thought to be the primary driver of the increased number of opioid-related overdose deaths since 2016. In fact, fentanyl and its analogues are involved in more than 70% of opioid-related overdoses. The standard opioid overdose rescue therapy naloxone is often insufficient to reverse opioid overdoses caused by fentalogue agonists under current treatment paradigms. However, the pharmacology of many fentalogues is unknown. Moreover, within the fentalogue series of compounds, it is possible that antagonists could be identified that might be superior to naloxone as opioid overdose reversal agents. In this report, we explore the pharmacology of 70 fentalogues and identify compounds that behave as MOR antagonists in vitro and demonstrate with one of these reversals of fentanyl-induced respiratory depression in the mouse. Such compounds could provide leads for the development of effective agents for the reversal of opioid overdose.

A Case Report of Delayed Opioid Toxidrome After Administration of Naloxone

Introduction

Opioid use is an epidemic that plagues the United States. Patients frequently present to the emergency department (ED) after opioid toxicity, which can lead to respiratory failure, apnea, and death. Although there is an effective antidote, naloxone, the current guidelines surrounding post-naloxone administration monitoring are loosely defined.

Case Report

We present a case in which an individual was administered naloxone after an intentional opioid overdose and was monitored for four hours, as is standard in our institution. He remained in the ED for additional workup following this observation period and subsequently experienced signs of severe respiratory depression, requiring bag-valve-mask ventilation, naloxone, and admission. Had he been discharged, as is typical after a four-hour observation period, the consequences could have been fatal. We present multiple theories as to why his opioid toxidrome may have presented in a delayed manner, including ingestion of fentanyl analogues and variability in metabolization of both opioids and naloxone. We also explore alternative overdose antidote products approved by the US Food and Drug Administration, which may impact post overdose care.

Conclusion

This case suggests that the correct amount of time to monitor patients after naloxone administration may be longer than originally thought. Our aim in this article was to further the discussion regarding the most appropriate observation period in cases of opioid toxicity.

Oxygen fluctuations in the brain and periphery induced by intravenous fentanyl: effects of dose and drug experience

Fentanyl is the leading contributor to drug overdose deaths in the United States. Its potency, rapid onset of action, and lack of effective reversal treatment make the drug much more lethal than other opioids. Although it is understood that fentanyl is dangerous at higher doses, the literature surrounding fentanyl's physiological effects remains contradictory at lower doses. To explore this discrepancy, we designed a study incorporating electrochemical assessment of oxygen in the brain (nucleus accumbens) and subcutaneous space, multisite thermorecording (brain, skin, muscle), and locomotor activity at varying doses of fentanyl (1.0, 3.0, 10, 30, and 90 µg/kg) in rats. In the nucleus accumbens, lower doses of fentanyl (3.0 and 10 µg/kg) led to an increase in oxygen levels while higher doses (30 and 90 µg/kg) led to a biphasic pattern, with an initial dose-dependent decrease followed by an increase. In the subcutaneous space, oxygen decreases started to appear at relatively lower doses (>3 µg/kg), had shorter onset latencies, and were stronger and prolonged. In the temperature experiment, lower doses of fentanyl (1.0, 3.0, and 10 µg/kg) led to an increase in brain, skin, and muscle temperatures, while higher doses (30 and 90 µg/kg) resulted in a dose-dependent biphasic temperature change, with an increase followed by a prolonged decrease. We also compared oxygen and temperature responses induced by fentanyl over six consecutive days and found no evidence of tolerance in both parameters. In conclusion, we report that fentanyl's effects are highly dose-dependent, drawing attention to the importance of better characterization to adequately respond in emergent cases of illicit fentanyl misuse.NEW & NOTEWORTHY By using electrochemical oxygen sensors in freely moving rats, we show that intravenous fentanyl induces opposite changes in brain oxygen at varying doses, increasing at lower doses (<10 µg/kg) and inducing a biphasic response, decrease followed by increase, at higher doses (>10-90 µg/kg). In contrast, fentanyl-induced dose-dependent oxygen decreases in the subcutaneous space. We consider the mechanisms underlying distinct oxygen responses in the brain and periphery and discuss naloxone's role in alleviating fentanyl-induced brain hypoxia.

From Friend to Foe: A Case of Naloxone-Induced Pulmonary Edema

Naloxone, an opioid receptor antagonist, effectively reverses opioid overdose and opioid-induced respiratory depression. A few side effects were reported after naloxone administration, including arrhythmia and pulmonary edema. Although rare, naloxone-induced pulmonary edema can be a severe and sometimes life-threatening complication requiring mechanical ventilation. This condition is predominantly linked to an upsurge in catecholamines after opioid reversal as part of acute withdrawal syndrome, especially seen in patients who chronically use opioids. In this report, we present a case of a 66-year-old patient who developed pulmonary edema following the administration of multiple doses of intravenous and intranasal naloxone for opioid overdose. This case highlights the potential adverse effects associated with naloxone use and discusses how to employ this life-saving medication with minimal side effects.

Evaluation and Optimization of a Microcavity Plate-Based Human Hepatocyte Spheroid Model for Predicting Clearance of Slowly Metabolized Drug Candidates

In vitro clearance assays are routinely conducted in drug discovery to predict in vivo clearance, but low metabolic turnover compounds are often difficult to evaluate. Hepatocyte spheroids can be cultured for days, achieving higher drug turnover, but have been hindered by limitations on cell number per well. Corning Elplasia microcavity 96-well microplates enable the culture of 79 hepatocyte spheroids per well. In this study, microcavity spheroid properties (size, hepatocyte function, longevity, culturing techniques) were assessed and optimized for clearance assays, which were then compared with microsomes, hepatocyte suspensions, two-dimensional-plated hepatocytes, and macrowell spheroids cultured as one per well. Higher enzyme activity coupled with greater hepatocyte concentrations in microcavity spheroids enabled measurable turnover of all 17 test compounds, unlike the other models that exhibited less drug turnover. Microcavity spheroids also predicted intrinsic clearance (CLint) and blood clearance (CLb) within threefold for 53% [9/17; average absolute fold error (AAFE), 3.9] and 82% (14/17; AAFE, 2.6) of compounds using a linear regression correction model, respectively. An alternate method incorporating mechanistic modeling that accounts for mass transport (permeability and diffusion) within spheroids demonstrated improved predictivity for CLint (12/17; AAFE, 4.0) and CLb (14/17; AAFE, 2.1) without the need for empirical scaling factors. The estimated fraction of drug metabolized by cytochrome P450 3A4 (fm,CYP3A4) using 3 μM itraconazole was within 25% of observed values for 6 of 8 compounds, with 5 of 8 compounds within 10%. In sum, spheroid cultures in microcavity plates permit the ability to test and predict clearance as well as fm,CYP3A4 of low metabolic turnover compounds and represent a valuable complement to conventional in vitro clearance assays. SIGNIFICANCE STATEMENT: Culturing multiple spheroids in ultralow attachment microcavities permits accurate quantitation of metabolically stable compounds in substrate depletion assays, overcoming limitations with singly cultured spheroids. In turn, this permits robust estimates of intrinsic clearance, which is improved with the consideration of mass transport within the spheroid. Incubations with 3 μM itraconazole enabled assessments of CYP3A4 involvement in hepatic clearance.

Fentanyl Overdose Causes Prolonged Cardiopulmonary Dysregulation in Male SKH1 Mice

Fentanyl overdose is a survivable condition that commonly resolves without chronic overt changes in phenotype. While the acute physiological effects of fentanyl overdose, such as opioid-induced respiratory depression (OIRD) and Wooden Chest Syndrome, represent immediate risks of lethality, little is known about longer-term systemic or organ-level impacts for survivors. In this study, we investigated the effects of a single, bolus fentanyl overdose on components of the cardiopulmonary system up to one week post. SKH1 mice were administered subcutaneous fentanyl at the highest non-lethal dose (62 mg/kg), LD10 (110 mg/kg), or LD50 (135 mg/kg), before euthanasia at 40 min, 6 h, 24 h, or 7 d post-exposure. The cerebral cortex, heart, lungs, and plasma were assayed using an immune monitoring 48-plex panel. The results showed significantly dysregulated cytokine, chemokine, and growth factor concentrations compared to time-matched controls, principally in hearts, then lungs and plasma to a lesser extent, for the length of the study, with the cortex largely unaffected. Major significant analytes contributing to variance included eotaxin-1, IL-33, and betacellulin, which were generally downregulated across time. The results of this study suggest that cardiopulmonary toxicity may persist from a single fentanyl overdose and have wide implications for the endurance of the expanding population of survivors.

An Autonomous Implantable Device for the Prevention of Death from Opioid Overdose

Opioid overdose accounts for nearly 75,000 deaths per year in the United States, representing a leading cause of mortality amongst the prime working age population (25-54 years). At overdose levels, opioid-induced respiratory depression becomes fatal without timely administration of the rescue drug naloxone. Currently, overdose survival relies entirely on bystander intervention, requiring a nearby person to discover and identify the overdosed individual, and have immediate access to naloxone to administer. Government efforts have focused on providing naloxone in abundance but do not address the equally critical component for overdose rescue: a willing and informed bystander. To address this unmet need, we developed the Naloximeter: a class of life-saving implantable devices that autonomously detect and treat overdose, with the ability to simultaneously contact first-responders. We present three Naloximeter platforms, for both fundamental research and clinical translation, all equipped with optical sensors, drug delivery mechanisms, and a supporting ecosystem of technology to counteract opioid-induced respiratory depression. In small and large animal studies, the Naloximeter rescues from otherwise fatal opioid overdose within minutes. This work introduces life-changing, clinically translatable technologies that broadly benefit a susceptible population recovering from opioid use disorder.

Perceptions on Treatment Utilization and Risk of Overdose Among Opioid Users in Kolkata: A Qualitative Study

Objective

This study was performed to explore the perceptions of treatment utilization patterns and the risk of overdose of both opioid users and their peer educators in Kolkata, India.

Methods

This study used a qualitative approach for data collection between September and December 2023. In-depth interviews (IDIs) of 20 opioid users from two authorized opioid substitution therapy (OST) centers (10 registered clients) and their respective field practice areas (10 unregistered clients) in Kolkata were conducted. Key informant interviews (KIIs) of six peer educators were also conducted. Semi-structured interviews were conducted; audio was recorded, transcribed, and translated for coding and analysis. An inductive thematic analysis was performed.

Results

Six broad themes (individual knowledge, logistics, legal/administrative, treatment effectiveness, self-confidence of treatment, and poor knowledge about the antidote of opioid poisoning, i.e., naloxone) emerged from the data analysis of IDIs. Four broad themes (high-risk behavior, raising awareness, the benefits of OST, and poor knowledge about naloxone) emerged from the data analysis of KIIs. Both opioid users and their peer educators were aware of the dangers of opioid overdose. However, they lacked sufficient knowledge in recognizing and offering immediate assistance in instances of opioid overdose, including the administration of naloxone.

Conclusion

The findings recognize the necessity of drawing and retaining opioid users in an efficient healthcare facility, such as OST centers, and providing them adequate training to identify and provide immediate assistance in cases of overdose, including naloxone administration. Our findings will assist policymakers in designing programs to prevent and treat opioid overdoses.

Searching for Synthetic Opioid Rescue Agents: Identification of a Potent Opioid Agonist with Reduced Respiratory Depression

While in the process of designing more effective synthetic opioid rescue agents, we serendipitously identified a new chemotype of potent synthetic opioid. Here, we report that conformational constraint of a piperazine ring converts a mu opioid receptor (MOR) antagonist into a potent MOR agonist. The prototype of the series, which we have termed atoxifent (2), possesses potent in vitro agonist activity. In mice, atoxifent displayed long-lasting antinociception that was reversible with naltrexone. Repeated dosing of atoxifent produced antinociceptive tolerance and a level of withdrawal like that of fentanyl. In rats, while atoxifent produced complete loss of locomotor activity like fentanyl, it failed to produce deep respiratory depression associated with fentanyl-induced lethality. Assessment of brain biodistribution demonstrated ample distribution of atoxifent into the brain with a Tmax of approximately 0.25 h. These results indicate enhanced safety for atoxifent-like molecules compared to fentanyl.

Combined treatment with naloxone and the alpha2 adrenoceptor antagonist atipamezole reversed brain hypoxia induced by a fentanyl-xylazine mixture in a rat model

Xylazine, a veterinary tranquillizer known by drug users as "Tranq", is being increasingly detected in people who overdose on opioid drugs, indicating enhanced health risk of fentanyl-xylazine mixtures. We recently found that xylazine potentiates fentanyl- and heroin-induced brain hypoxia and eliminates the rebound-like post-hypoxic oxygen increases. Here, we used oxygen sensors coupled with high-speed amperometry in rats of both sexes to explore the treatment potential of naloxone plus atipamezole, a selective α2-adrenoceptor antagonist, in reversing brain (nucleus accumbens) and periphery (subcutaneous space) hypoxia induced by a fentanyl-xylazine mixture. Pretreatment with naloxone (0.2 mg/kg, IV) fully blocked brain and peripheral hypoxia induced by fentanyl (20 μg/kg, IV), but only partially decreased hypoxia induced by a fentanyl-xylazine mixture. Pretreatment with atipamezole (0.25 mg/kg, IV) fully blocked the hypoxic effects of xylazine (1.0 mg/kg, IV), but not fentanyl. Pretreatment with atipamezole + naloxone was more potent than naloxone alone in blocking the hypoxic effects of the fentanyl-xylazine mixture. Both naloxone and naloxone + atipamezole, delivered at the peak of brain hypoxia (3 min post fentanyl-xylazine exposure), reversed the rapid initial brain hypoxia, but only naloxone + atipamezole decreased the prolonged weaker hypoxia. There were no sex differences in the effects of the different drugs and their combinations on brain and peripheral oxygen responses. Results indicate that combined treatment with naloxone and atipamezole is more effective than naloxone alone in reversing the hypoxic effects of fentanyl-xylazine mixtures. Naloxone + atipamezole treatment should be considered in preventing overdoses induced by fentanyl-xylazine mixtures in humans.

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.

Missouri's Overdose Field Report: descriptive analysis, survival trends, and naloxone dosing patterns from a community-based survey tool, 2018-2022

Background: Missouri's Overdose Field Report (ODFR) is a community-based reporting system which intends to capture overdoses which may not be otherwise recorded.Objectives: Describe the factors related to non-fatal overdoses reported to Missouri's ODFR.Methods: This study used a descriptive epidemiological approach to examine the demographics and circumstances of overdoses reported to the ODFR. We used binary logistic regression to evaluate factors associated with survival and ordinal logistic regression to evaluate factors associated with number of doses used. Factors were chosen based on their relevance to overdose education and survival, and naloxone distribution.Results: Between 2018 and 2022, 12,225 overdoses (67% male; 78% White) were reported through the ODFR, with a 96% (n = 11,225) survival rate. Overdose survival (ps < .02) was associated with younger age (OR = .58), no opioid and stimulant co-involvement (OR = .61), and private location (OR = .48). Intramuscular naloxone in particular was associated with a significantly higher odds of survival compared to nasal naloxone (OR = 2.11). An average of 1.6 doses of naloxone per incident were administered. Additional doses were associated (ps < .02) with being older (OR = .45), female (OR = .90), nasal naloxone (versus intravenous) (OR = .65), and the belief fentanyl was present (OR = 1.49).Conclusion: Our reporting form provides a comprehensive picture of the events surrounding reported overdoses, including factors associated with survival, how much naloxone was used, and the effects of respondents believing fentanyl was involved. Missouri's report can provide support for current naloxone dosing, contextualize refusing post-overdose transport, and can be used to improve overdose response by community and first responders.

Development of fentanyl-specific monoclonal antibody (mAb) to antagonize the pharmacological effects of fentanyl

Fentanyl, a critical component of opioid analgesics, poses a severe threat to public health, exacerbating the drug problem due to its potential fatality. Herein, we present two novel haptens designed with different attachment sites conjugated to keyhole limpet hemocyanin (KLH), aiming to develop an efficacious vaccine against fentanyl. KLH-Fent-1 demonstrated superior performance over KLH-Fent-2 in antibody titer, blood-brain distribution, and antinociceptive tests. Consequently, we immunized mice with KLH-Fent-1 to generate fentanyl-specific monoclonal antibodies (mAbs) using the hybridoma technique to compensate for the defects of active immunization in the treatment of opioid overdose and addiction. The mAb produced by hybridoma 9D5 exhibited the ability to recognize fentanyl and its analogs with a binding affinity of 10-10 M. Subsequently, we developed a human IgG1 chimeric mAb to improve the degree of humanization. Pre-treatment with murine and chimeric mAb significantly reduced the analgesic effect of fentanyl and altered its blood-brain biodistribution in vivo. Furthermore, in a mouse model of fentanyl-induced respiratory depression, the chimeric mAb effectively reversed respiratory depression promptly and maintained a certain level during the week. The development of high-affinity chimeric mAb gives support to combat the challenges of fentanyl misuse and its detrimental consequences. In conclusion, mAb passive immunization represents a viable strategy for addressing fentanyl addiction and overdose.

Fentanyl and its derivatives: Pain-killers or man-killers?

Fentanyl is a synthetic μ-opioid receptor agonist approved to treat severe to moderate pain with faster onset of action and about 100 times more potent than morphine. Over last two decades, abuse of fentanyl and its derivatives has an increased trend, globally. Currently, the United States (US) faces the most serious situation related to fentanyl overdose, commonly referred to as the opioid epidemic. Nowadays, fentanyl is considered as the number one cause of death for adults aged 18-45 in the US. Synthesis and derivatization of fentanyl is inexpensive to manufacture and easily achievable. Indeed, more than 1400 fentanyl derivatives have been described in the scientific literature and patents. In addition, accessibility and efficacy of fentanyl and its derivatives can play a potential role in misuse of these compounds as a chemical weapon. In this review, the properties, general pharmacology, and overdose death cases associated with fentanyl and selected derivatives are presented. Moreover, current opioid epidemic in the US, Moscow theatre hostage crisis, and potential misuse of fentanyl and its derivatives as a chemical weapon are disclosed.

Is a randomised controlled trial of take home naloxone distributed in emergency settings likely to be feasible and acceptable? Findings from a UK qualitative study exploring perspectives of people who use opioids and emergency services staff

OBJECTIVE

Distribution of take-home naloxone (THN) by emergency services may increase access to THN and reduce deaths and morbidity from opioid overdose. As part of a feasibility study for a randomised controlled trial (RCT) of distribution of THN kits and education within ambulance services and Emergency Departments (EDs), we used qualitative methods to explore key stakeholders' perceptions of feasibility and acceptability of delivering the trial.

METHODS

We undertook semi-structured interviews and focus groups with 26 people who use opioids and with 20 paramedics and ED staff from two intervention sites between 2019 and 2021. Interviews and focus groups were recorded, transcribed verbatim and analysed using Framework Analysis.

RESULTS

People using opioids reported high awareness of overdose management, including personal experience of THN use. Staff perceived emergency service provision of THN as a low-cost, low-risk intervention with potential to reduce mortality, morbidity and health service use. Staff understood the trial aims and considered it compatible with their work. All participants supported widening access to THN but reported limited trial recruitment opportunities partly due to difficulties in consenting patients during overdose. Procedural problems, restrictive recruitment protocols, limited staff buy-in and patients already owning THN limited trial recruitment. Determining trial effectiveness was challenging due to high levels of alternative community provision of THN.

CONCLUSIONS

Distribution of THN in emergency settings was considered feasible and acceptable for stakeholders but an RCT to establish the effectiveness of THN delivery is unlikely to generate further useful evidence due to difficulties in recruiting patients and assessing benefits.

Model of negative affect induced by withdrawal from acute and chronic morphine administration in male mice

Opioid use disorder (OUD) is a chronic relapsing disorder that is a major burden for the lives of affected individuals, and society as a whole. Opioid withdrawal is characterized by strong physical symptoms, along with signs of negative affect. Negative affect due to opioid withdrawal is a major obstacle to recovery and relapse prevention. The mechanisms behind negative affect due to either spontaneous or antagonist-precipitated opioid withdrawal are not well known, and more animal models need be developed. Here, we present behavioral models of negative affect upon naloxone-precipitated morphine withdrawal in adult male mice. Social, anxiety, and despair-like deficits were investigated following naloxone administration in mice receiving morphine under three dosing regimens; acute, chronic constant dose and chronic escalating doses. Social behaviour in the three-chamber social preference test was decreased following withdrawal from chronic and escalating but not acute morphine. Anxiety-like behaviour in the open field was increased for all three treatments. Despair-like behaviour was increased following withdrawal from chronic and escalating but not acute morphine. Altogether, these animal models will contribute to study behavioural and neuronal circuitries involved in the several negative affective signs characterizing OUD.

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.

Fentanyl overdose: Temporal effects and prognostic factors in SKH1 mice

Fentanyl exposure and overdose are growing concerns in public health and occupational safety. This study aimed to establish parameters of fentanyl lethality in SKH1 mice for future overdose research. Lethality was determined using the up-down procedure, with subjects monitored post-administration using pulse oximetry (5 min) and then whole-body plethysmography (40 min). Following the determination of subcutaneous dose-response, [18F]Fluorodeoxyglucose positron emission tomography (18 F-FDG PET) was performed after LD10 fentanyl at 40 min, 6 h, 24 h or 7 days post-dose. LD10 and LD50 were observed to be 110 and 135 mg/kg, respectively, and consistent with four-parameter logistic fit values of 111.2 and 134.6 mg/kg (r2  = 0.9996). Overdose (LD10 or greater) yielded three distinct cardiovascular groups: survival, non-survival with blood oxygen saturation (SpO2) minimum ≥37% and non-survival with SpO2 <37%. Breaths per minute, minute volume and inspiratory quotient were significantly different between surviving and non-surviving animals for up to 40 min post-injection. 18 F-FDG PET revealed decreased glucose uptake in the heart, lungs and brain for up to 24 h. These findings provide critical insights into fentanyl lethality in SKH1 mice, including non-invasive respiratory effects and organ-specific impacts that are invaluable for future translational studies investigating the temporal effects of fentanyl overdose.

Xylazine suppresses fentanyl consumption during self-administration and induces a unique sex-specific withdrawal syndrome that is not altered by naloxone in rats

Prescription and illicit opioid use are a public health crisis, with the landscape shifting to fentanyl use. Since fentanyl is 100-fold more potent than morphine, its use is associated with a higher risk of fatal overdose that can be remediated through naloxone (Narcan) administration. However, recent reports indicate that xylazine, an anesthetic, is increasingly detected in accidental fentanyl overdose deaths. Anecdotal reports suggest that xylazine may prolong the fentanyl "high," alter the onset of fentanyl withdrawal, and increase resistance to naloxone-induced reversal of overdose. To date, no preclinical studies have evaluated the impacts of xylazine on fentanyl self-administration (SA; 2.5 μg/kg/infusion) or withdrawal to our knowledge. We established a rat model of xylazine/fentanyl co-SA and withdrawal and evaluated outcomes as a function of biological sex. When administered alone, chronic xylazine (2.5 mg/kg, intraperitoneal) induced unique sex-specific withdrawal symptomatology, whereby females showed delayed onset of signs and a possible enhancement of sensitivity to the motor-suppressing effects of xylazine. Xylazine reduced fentanyl consumption in both male and female rats regardless of whether it was experimenter-administered or added to the intravenous fentanyl product (0.05, 0.10, and 0.5 mg/kg/infusion) when compared to fentanyl SA alone. Interestingly, this effect was dose-dependent when self-administered intravenously. Naloxone (0.1 mg/kg, subcutaneous injection) did not increase somatic signs of fentanyl withdrawal, regardless of the inclusion of xylazine in the fentanyl infusion in either sex; however, somatic signs of withdrawal were higher across time points in females after xylazine/fentanyl co-SA regardless of naloxone exposure as compared to females following fentanyl SA alone. Together, these results indicate that xylazine/fentanyl co-SA dose-dependently suppressed fentanyl intake in both sexes and induced a unique withdrawal syndrome in females that was not altered by acute naloxone treatment. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Acute opioid overdose in pediatric patients

Recent increases in pediatric and adolescent opioid fatalities mandate an urgent need for early consideration of possible opioid exposure and specific diagnostic and management strategies and interventions tailored to these unique populations. In contrast to adults, pediatric methods of exposure include accidental ingestions, prescription misuse, and household exposure. Early recognition, appropriate diagnostic evaluation, along with specialized treatment for opioid toxicity in this demographic are discussed. A key focus is on Naloxone, an essential medication for opioid intoxication, addressing its unique challenges in pediatric use. Unique pediatric considerations include recognition of accidental ingestions in our youngest population, critical social aspects including home safety and intentional exposure, and harm reduction strategies, mainly through Naloxone distribution and education on safe medication practices. It calls for a multifaceted approach, including creating pediatric-specific guidelines, to combat the opioid crisis among children and to work to lower morbidity and mortality from opioid overdoses.

Multimodal Acute Pain Management in the Parturient with Opioid Use Disorder: A Review

The opioid epidemic in the United States has led to an increasing number of pregnant patients with opioid use disorder (OUD) presenting to obstetric units. Caring for this complex patient population requires an interdisciplinary approach involving obstetricians, anesthesiologists, addiction medicine physicians, psychiatrists, and social workers. The management of acute pain in the parturient with OUD can be challenging due to several factors, including respiratory depression, opioid tolerance, and opioid-induced hyperalgesia. Patients with a history of OUD can present in one of three categories: 1) those with untreated OUD; 2) those who are currently abstinent from opioids; 3) those being treated with medications to prevent withdrawal. A patient-centered, multimodal approach is essential for optimal peripartum pain relief and prevention of adverse maternal and neonatal outcomes. Medications for opioid use disorder (MOUD), previously referred to as medication-assisted therapy (MAT), include opioids like methadone, buprenorphine, and naltrexone. These are prescribed for pregnant patients with OUD, but appropriate dosing and administration of these medications are critical to avoid withdrawal in the mother. Non-opioid analgesics such as acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) can be used in a stepwise approach, and regional techniques like neuraxial anesthesia and truncal blocks offer opioid-sparing options. Other medications like ketamine, clonidine, dexmedetomidine, nitrous oxide, and gabapentinoids show promise for pain management but require further research. Overall, a comprehensive pain management strategy is essential to ensure the well-being of both the mother and the fetus in pregnant patients with OUD.

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.

Impact of the Narcotics Information Management System on Opioid Use Among Outpatients With Musculoskeletal and Connective Tissue Disorders: Quasi-Experimental Study Using Interrupted Time Series

BACKGROUND

Opioids have traditionally been used to manage acute or terminal pain. However, their prolonged use has the potential for abuse, misuse, and addiction. South Korea introduced a new health care IT system named the Narcotics Information Management System (NIMS) with the objective of managing all aspects of opioid use, including manufacturing, distribution, sales, disposal, etc.

OBJECTIVE

This study aimed to assess the impact of NIMS on opioid use.

METHODS

We conducted an analysis using national claims data from 45,582 patients diagnosed with musculoskeletal and connective tissue disorders between 2016 and 2020. Our approach included using an interrupted time-series analysis and constructing segmented regression models. Within these models, we considered the primary intervention to be the implementation of NIMS, while we treated the COVID-19 outbreak as the secondary event. To comprehensively assess inappropriate opioid use, we examined 4 key indicators, as established in previous studies: (1) the proportion of patients on high-dose opioid treatment, (2) the proportion of patients receiving opioid prescriptions from multiple providers, (3) the overlap rate of opioid prescriptions per patient, and (4) the naloxone use rate among opioid users.

RESULTS

During the study period, there was a general trend of increasing opioid use. After the implementation of NIMS, significant increases were observed in the trend of the proportion of patients on high-dose opioid treatment (coefficient=0.0271; P=.01) and in the level of the proportion of patients receiving opioid prescriptions from multiple providers (coefficient=0.6252; P=.004). An abrupt decline was seen in the level of the naloxone use rate among opioid users (coefficient=-0.2968; P=.04). While these changes were statistically significant, their clinical significance appears to be minor. No significant changes were observed after both the implementation of NIMS and the COVID-19 outbreak.

CONCLUSIONS

This study suggests that, in its current form, the NIMS may not have brought significant improvements to the identified indicators of opioid overuse and misuse. Additionally, the COVID-19 outbreak exhibited no significant influence on opioid use patterns. The absence of real-time monitoring feature within the NIMS could be a key contributing factor. Further exploration and enhancements are needed to maximize the NIMS' impact on curbing inappropriate opioid use.

Are carfentanil and acrylfentanyl naloxone resistant?

The rapid rise in deaths since 2012 due to opioid poisoning is correlated with the proliferation of potent synthetic opioid agonists such as fentanyl, acrylfentanyl, and carfentanil. The efficacy of frontline antidotes such as naloxone in reversing such poisoning events has been questioned, and the possibility of naloxone-resistant synthetic opioids has been raised. In this manuscript, we applied in vitro techniques to establish the median effective inhibitory concentrations for fentanyl, acrylfentanyl, and carfentanil and subsequently evaluate naloxone's ability to reverse agonist-receptor interactions.

"We don't even know where it's kept": exploring perspectives on naloxone administration by provincial correctional workers in Manitoba, Canada

PURPOSE

Prisonersare at disproportionate risk of suffering substance-related harms. The administration of naloxone is essential to reversing opioid overdose and minimizing substance-related harms in prison and the community. The purpose of this study is to examine how naloxone administration is practiced and perceived in prison settings.

DESIGN/METHODOLOGY/APPROACH

The authors conducted surveys with correctional workers in Manitoba, Canada (n = 257) to examine how they understand and feel about the need for and practice of administering naloxone in their everyday work with criminalized populations.

FINDINGS

Respondents reported feeling a great need to administer naloxone, but most did not feel adequately trained to administer naloxone, creating the perception that criminalized populations remain at enhanced risk.

ORIGINALITY/VALUE

Findings provide emerging evidence of the need for training and accompanying policies and procedures for correctional workers on how to access and administer naloxone.

Top 25 Medications the Plastic and Reconstructive Surgery Trainee Should Know for an Emergency Medicine Department Consult

SUMMARY

Plastic surgery trainees are often called to render care in the emergency department (eg, for established patients, trauma, burns). Broad-based knowledge in pharmacotherapeutics during these encounters is critical. This includes an understanding of pain medications, anxiolytics, local anesthetics, antibiotics, anticoagulants, antidotes, and more to ensure optimal patient care. The purpose of this report is to describe 25 frequently used and other important medications that plastic surgery trainees should know for an adult emergency department encounter.

Brain oxygen responses induced by opioids: focus on heroin, fentanyl, and their adulterants

Opioids are important tools for pain management, but abuse can result in serious health complications. Of these complications, respiratory depression that leads to brain hypoxia is the most dangerous, resulting in coma and death. Although all opioids at large doses induce brain hypoxia, danger is magnified with synthetic opioids such as fentanyl and structurally similar analogs. These drugs are highly potent, act rapidly, and are often not effectively treated by naloxone, the standard of care for opioid-induced respiratory depression. The goal of this review paper is to present and discuss brain oxygen responses induced by opioids, focusing on heroin and fentanyl. In contrast to studying drug-induced changes in respiratory activity, we used chronically implanted oxygen sensors coupled with high-speed amperometry to directly evaluate physiological and drug-induced fluctuations in brain oxygen levels in awake, freely moving rats. First, we provide an overview of brain oxygen responses to physiological stimuli and discuss the mechanisms regulating oxygen entry into brain tissue. Next, we present data on brain oxygen responses induced by heroin and fentanyl and review underlying mechanisms. These data allowed us to compare the effects of these drugs on brain oxygen in terms of their potency, time-dependent response pattern, and potentially lethal effect at high doses. Then, we present the interactive effects of opioids during polysubstance use (alcohol, ketamine, xylazine) on brain oxygenation. Finally, we consider factors that affect the therapeutic potential of naloxone, focusing on dosage, timing of drug delivery, and contamination of opioids by other neuroactive drugs. The latter issue is considered chiefly with respect to xylazine, which strongly potentiates the hypoxic effects of heroin and fentanyl. Although this work was done in rats, the data are human relevant and will aid in addressing the alarming rise in lethality associated with opioid misuse.

Intranasal Naloxone for Opioid Overdose

This JAMA Insights describes indications for naloxone use in preventing opioid overdoses and benefits vs barriers to its availability following FDA approval of its availability without a prescription.