Population pharmacokinetics of intravenous, intramuscular, and intranasal naloxone in human volunteers

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.

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.

Opioid Overdose: Limitations in Naloxone Reversal of Respiratory Depression and Prevention of Cardiac Arrest

Opioids are effective analgesics, but they can have harmful adverse effects, such as addiction and potentially fatal respiratory depression. Naloxone is currently the only available treatment for reversing the negative effects of opioids, including respiratory depression. However, the effectiveness of naloxone, particularly after an opioid overdose, varies depending on the pharmacokinetics and the pharmacodynamics of the opioid that was overdosed. Long-acting opioids, and those with a high affinity at the µ-opioid receptor and/or slow receptor dissociation kinetics, are particularly resistant to the effects of naloxone. In this review, the authors examine the pharmacology of naloxone and its safety and limitations in reversing opioid-induced respiratory depression under different circumstances, including its ability to prevent cardiac arrest.

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.

Re-examining Naloxone Pharmacokinetics After Intranasal and Intramuscular Administration Using the Finite Absorption Time Concept

BACKGROUND AND OBJECTIVES

Naloxone for opioid overdose treatment can be administered by intravenous injection, intramuscular injection, or intranasal administration. Published data indicate differences in naloxone pharmacokinetics depending on the route of administration. The aim of this study was to analyze pharmacokinetic data in the same way that we recently successfully applied the concept of the finite absorption time in orally administered drug formulations.

METHODS

Using the model equations already derived, we performed least squares analysis on 24 sets of naloxone concentration in the blood as a function of time.

RESULTS

We found that intramuscular and intranasal administration can be described more accurately when considering zero-order absorption kinetics for finite time compared with classical first order absorption kinetics for infinite time.

CONCLUSIONS

One-compartment models work well for most cases. Two-compartment models provide better details, but have higher parameter uncertainties. The absorption duration can be determined directly from the model parameters and thus allow an easy comparison between the ways of administration. Furthermore, the precise site of injection for intramuscular delivery appears to make a difference in terms of the duration of the drug absorption.

Population pharmacokinetics of buprenorphine and naloxone sublingual combination in Chinese healthy volunteers and patients with opioid use disorder: Model-based dose optimization

The sublingual combination of buprenorphine (BUP) and naloxone (NLX) is a new treatment option for opioid use disorder (OUD) and is effective in preventing drug abuse. This study aimed to explore rational dosing regimen for OUD patients in China via a model-based dose optimization approach. BUP, norbuprenorphine (norBUP), and NLX plasma concentrations of 34 healthy volunteers and 12 OUD subjects after single or repeated dosing were included. A parent-metabolite population pharmacokinetics (popPK) model with transit compartments for absorption was implemented to describe the pharmacokinetic profile of BUP-norBUP. In addition, NLX concentrations were well captured by a one-compartment popPK model. Covariate analysis showed that every additional swallow after the administration within the observed range (0-12) resulted in a 3.5% reduction in BUP bioavailability. This provides a possible reason for the less-than-dose proportionality of BUP. There were no differences in the pharmacokinetic characteristics between BUP or NLX in healthy volunteers and OUD subjects. Ethnic sensitivity analysis demonstrated that the dose-normalized peak concentration and area-under-the-curve of BUP in Chinese were about half of Puerto Ricans, which was consistent with a higher clearance observed in Chinese (166 L / h vs. 270 L / h ). Furthermore, Monte Carlo simulations showed that an 8 mg three-times daily dose was the optimized regimen for Chinese OUD subjects. This regimen ensured that opioid receptor occupancy remained at a maximum (70%) in more than 95% of subjects, at the same time, with NLX plasma concentrations below the withdrawal reaction threshold (4.6  n g / m L ).

Nanogels as Novel Nanocarrier Systems for Efficient Delivery of CNS Therapeutics

Nanogels have come out as a great potential drug delivery platform due to its prominently high colloidal stability, high drug loading, core-shell structure, good permeation property and can be responsive to environmental stimuli. Such nanoscopic drug carriers have more excellent abilities over conventional nanomaterials for permeating to brain parenchyma in vitro and in vivo. Nanogel-based system can be nanoengineered to bypass physiological barriers via non-invasive treatment, rendering it a most suitable platform for the management of neurological conditions such as neurodegenerative disorders, brain tumors, epilepsy and ischemic stroke, etc. Therapeutics of central nervous system (CNS) diseases have shown marked limited site-specific delivery of CNS by the poor access of various drugs into the brain, due to the presences of the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCSFB). Hence, the availability of therapeutics delivery strategies is considered as one of the most major challenges facing the treatment of CNS diseases. The primary objective of this review is to elaborate the newer advances of nanogel for CNS drugs delivery, discuss the early preclinical success in the field of nanogel technology and highlight different insights on its potential neurotoxicity.

Pharmacokinetic considerations for community-based dosing of nasal naloxone in opioid overdose in adults

INTRODUCTION

The administration of the opioid antagonist naloxone in the community is a measure to prevent death from opioid overdose. Approved nasal naloxone sprays deliver initial doses of 0.9 to 8 mg. The level of the initial community dose is controversial, as the scientific base is weak.In this review knowledge of the pharmacokinetics of nasal, both approved and improvised nasal sprays, and intramuscular naloxone will be utilized to evaluate dose-effect relationships in previous studies of opioid overdose outcomes.

AREAS COVERED

The aim was to present scientifically based considerations on the initial nasal naloxone doses currently available, which reasonably balances the effect and adverse outcomes, given that at least two doses are at hand. Also included in these considerations is the challenge by illicitly manufactured fentanyl and analogs.This paper is based on both peer-reviewed and grey literature identified by several searches, of such as naloxone pharmacokinetics/formulations/outcomes/emergency medical services, in PubMed and Embase.

EXPERT OPINION

There is little scientific evidence that supports the use of initial systemic dosing that exceeds 0.8 mg in the community. Higher doses increase the risk of withdrawal symptoms feared in people who use opioids. Many obstacles may reduce the potential of community-administered naloxone.

Microneedle-mediated transdermal delivery of naloxone hydrochloride for treatment of opioid overdose

Naloxone (NAL) is administered parenterally or intranasally for treating opioid overdose. The short duration of action of NAL calls for frequent re-dosing which may be eliminated by the development of a transdermal system. This study aimed to assess the effect of microneedles on improving the skin permeation of NAL hydrochloride. In vitro permeation of NAL across intact and microneedle-treated (Dr. Pen™ Ultima A6) porcine skin was evaluated. The effect of microneedle length and application duration, and donor concentration on NAL permeation were investigated. In-vitro in-vivo correlation of the permeation results was done to predict the plasma concentration kinetics of NAL in patients. In vitro passive permeation of NAL after 6 h was observed to be 8.25±1.06 µg/cm². A 56- and 37-fold enhancement was observed with 500 and 250 µm needles applied for 1 min, respectively. Application of 500 µm MNs for 2 min significantly reduced the lag time to ~ 8 min and increasing the donor concentration for the same treatment group doubled the permeation (p < 0.05). Modeling simulations demonstrated the attainment of pharmacokinetic profile of NAL comparable to those obtained with the FDA-approved intramuscular and intranasal devices. Microneedle-mediated transdermal delivery holds potential for rapid and sustained NAL delivery for opioid overdose treatment.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

High-dose naloxone: Effects by late administration on pain and hyperalgesia following a human heat injury model. A randomized, double-blind, placebo-controlled, crossover trial with an enriched enrollment design

Severe chronic postsurgical pain has a prevalence of 4–10% in the surgical population. The underlying nociceptive mechanisms have not been well characterized. Following the late resolution phase of an inflammatory injury, high-dose μ-opioid-receptor inverse agonists reinstate hypersensitivity to nociceptive stimuli. This unmasking of latent pain sensitization has been a consistent finding in rodents while only observed in a limited number of human volunteers. Latent sensitization could be a potential triggering venue in chronic postsurgical pain. The objective of the present trial was in detail to examine the association between injury-induced secondary hyperalgesia and naloxone-induced unmasking of latent sensitization. Healthy volunteers (n = 80) received a cutaneous heat injury (47°C, 420 s, 12.5 cm²). Baseline secondary hyperalgesia areas were assessed 1 h post-injury. Utilizing an enriched enrollment design, subjects with a magnitude of secondary hyperalgesia areas in the upper quartile (‘high-sensitizers’ [n = 20]) and the lower quartile (‘low-sensitizers’ [n = 20]) were selected for further study. In four consecutive experimental sessions (Sessions 1 to 4), the subjects at two sessions (Sessions 1 and 3) received a cutaneous heat injury followed 168 h later (Sessions 2 and 4) by a three-step target-controlled intravenous infusion of naloxone (3.25 mg/kg), or normal saline. Assessments of secondary hyperalgesia areas were made immediately before and stepwise during the infusions. Simple univariate statistics revealed no significant differences in secondary hyperalgesia areas between naloxone and placebo treatments (P = 0.215), or between ‘high-sensitizers’ and ‘low-sensitizers’ (P = 0.757). In a mixed-effects model, secondary hyperalgesia areas were significantly larger following naloxone as compared to placebo for ‘high-sensitizers’ (P < 0.001), but not ‘low-sensitizers’ (P = 0.651). Although we could not unequivocally demonstrate naloxone-induced reinstatement of heat injury-induced hyperalgesia, further studies in clinical postsurgical pain models are warranted.

Protocol for Take-home naloxone In Multicentre Emergency (TIME) settings: feasibility study

Background

Opioids, such as heroin, kill more people worldwide by overdose than any other type of drug, and death rates associated with opioid poisoning in the UK are at record levels (World Drug Report 2018 [Internet]. [cited 2019 Nov 19]. Available from: http://www.unodc.org/wdr2018/; Deaths related to drug poisoning in England and Wales - Office for National Statistics [Internet]. [cited 2019 Nov 19]. Available from: https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/deaths/bulletins/deathsrelatedtodrugpoisoninginenglandandwales/2018registrations). Naloxone is an opioid antagonist which can be distributed in ‘kits’ for administration by witnesses in an overdose emergency. This intervention is known as take-home naloxone (THN). We know that THN can save lives on an individual level, but there is currently limited evidence about the effectiveness of THN distribution on an aggregate level, in specialist drug service settings or in emergency service settings. Notably, we do not know whether THN kits reduce deaths from opioid overdose in at-risk populations, if there are unforeseen harms associated with THN distribution or if THN is cost-effective. In order to address this research gap, we aim to determine the feasibility of a fully powered cluster randomised controlled trial (RCT) of THN distribution in emergency settings.

Methods

We will carry out a feasibility study for a RCT of THN distributed in emergency settings at four sites, clustered by Emergency Department (ED) and catchment area within its associated ambulance service. THN is a peer-administered intervention. At two intervention sites, emergency ambulance paramedics and ED clinical staff will distribute THN to adult patients who are at risk of opioid overdose. At two control sites, practice will carry on as usual. We will develop a method of identifying a population to include in an evaluation, comprising people at risk of fatal opioid overdose, who may potentially receive naloxone included in a THN kit.

We will gather anonymised outcomes up to 1 year following a 12-month ‘live’ trial period for patients at risk of death from opioid poisoning. We expect approximately 100 patients at risk of opioid overdose to be in contact with each service during the 1-year recruitment period. Our outcomes will include deaths, emergency admissions, intensive care admissions, and ED attendances. We will collect numbers of eligible patients attended by participating in emergency ambulance paramedics and attending ED, THN kits issued, and NHS resource usage. We will determine whether to progress to a fully powered trial based on pre-specified progression criteria: sign-up of sites (n = 4), staff trained (≥ 50%), eligible participants identified (≥ 50%), THN provided to eligible participants (≥ 50%), people at risk of death from opioid overdose identified for inclusion in follow-up (≥ 75% of overdose deaths), outcomes retrieved for high-risk individuals (≥ 75%), and adverse event rate (< 10% difference between study arms).

Discussion

This feasibility study is the first randomised, methodologically robust investigation of THN distribution in emergency settings. The study addresses an evidence gap related to the effectiveness of THN distribution in emergency settings. As this study is being carried out in emergency settings, obtaining informed consent on behalf of participants is not feasible. We therefore employ novel methods for identifying participants and capturing follow-up data, with effectiveness dependent on the quality of the available routine data.

Trial registration

ISRCTN13232859 (Registered 16/02/2018)

Higher naloxone dosing in a quantitative systems pharmacology model that predicts naloxone-fentanyl competition at the opioid mu receptor level

Rapid resuscitation of an opioid overdose with naloxone, an opioid antagonist, is critical. We developed an opioid receptor quantitative systems pharmacology (QSP) model for evaluation of naloxone dosing. In this model we examined three opioid exposure levels that have been reported in the literature (25 ng/ml, 50 ng/ml, and 75 ng/ml of fentanyl). The model predicted naloxone-fentanyl interaction at the mu opioid receptor over a range of three naloxone doses. For a 2 mg intramuscular (IM) dose of naloxone at lower fentanyl exposure levels (25 ng/ml and 50 ng/ml), the time to decreasing mu receptor occupancy by fentanyl to 50% was 3 and 10 minutes, respectively. However, at a higher fentanyl exposure level (75 ng/ml), a dose of 2 mg IM of the naloxone failed to reduce mu receptor occupancy by fentanyl to 50%. In contrast, naloxone doses of 5 mg and 10 mg IM reduced mu receptor occupancy by fentanyl to 50% in 5.5 and 4 minutes respectively. These results suggest that the current doses of naloxone (2 mg IM or 4 mg intranasal (IN)) may be inadequate for rapid reversal of toxicity due to fentanyl exposure and that increasing the dose of naloxone is likely to improve outcomes.

Treatment of acute naloxone-precipitated opioid withdrawal with buprenorphine

Naloxone is a frequently utilized and effective treatment to reverse the life-threatening effects of illicit opioid intoxication. Excessive naloxone dosing in these circumstances, however, may lead to naloxone-precipitated opioid withdrawal in individuals with opioid dependence. Buprenorphine, a partial mu-opioid agonist, is increasingly utilized in the Emergency Department (ED) for the treatment of opioid withdrawal syndrome but little is known regarding its utility in cases of naloxone-precipitated opioid withdrawal. We report a case of naloxone-precipitated opioid withdrawal that was effectively treated with sublingual buprenorphine. An older male was brought into the ED with signs and symptoms of opioid toxicity that was successfully treated with pre-hospital naloxone by Emergency Medical Services. He had a clinical opioid withdrawal scale (COWS) or 10 with abdominal cramping and unintentional defecation. After a discussion of treatment options and possible adverse effects with the patient, the decision was made to administer 4 mg/1 mg of sublingual buprenorphine/naloxone film. The patient reported a rapid improvement in symptoms and at 30 min posttreatment, his COWS was 4. His COWS decreased to 3 at 1 h and this was sustained for 4 h of observation. The patient was subsequently discharged to a treatment facility for opioid use disorder. This case highlights the potential of buprenorphine as a treatment modality for acute naloxone-precipitated opioid withdrawal. Due to the risks of worsening or sustained buprenorphine-precipitated opioid withdrawal, further research is warranted to identify patients who may benefit from this therapy.

Effect of Intranasal vs Intramuscular Naloxone on Opioid Overdose: A Randomized Clinical Trial

IMPORTANCE

Previous unblinded clinical trials suggested that the intranasal route of naloxone hydrochloride was inferior to the widely used intramuscular route for the reversal of opioid overdose.

OBJECTIVE

To test whether a dose of naloxone administered intranasally is as effective as the same dose of intramuscularly administered naloxone in reversing opioid overdose.

DESIGN, SETTING, AND PARTICIPANTS

A double-blind, double-dummy randomized clinical trial was conducted at the Uniting Medically Supervised Injecting Centre in Sydney, Australia. Clients of the center were recruited to participate from February 1, 2012, to January 3, 2017. Eligible clients were aged 18 years or older with a history of injecting drug use (n = 197). Intention-to-treat analysis was performed for all participants who received both intranasal and intramuscular modes of treatment (active or placebo).

INTERVENTIONS

Clients were randomized to receive 1 of 2 treatments: (1) intranasal administration of naloxone hydrochloride 800 μg per 1 mL and intramuscular administration of placebo 1 mL or (2) intramuscular administration of naloxone hydrochloride 800 μg per 1 mL and intranasal administration of placebo 1 mL.

MAIN OUTCOMES AND MEASURES

The primary outcome measure was the need for a rescue dose of intramuscular naloxone hydrochloride (800 μg) 10 minutes after the initial treatment. Secondary outcome measures included time to adequate respiratory rate greater than or equal to 10 breaths per minute and time to Glasgow Coma Scale score greater than or equal to 13.

RESULTS

A total of 197 clients (173 [87.8%] male; mean [SD] age, 34.0 [7.82] years) completed the trial, of whom 93 (47.2%) were randomized to intramuscular naloxone dose and 104 (52.8%) to intranasal naloxone dose. Clients randomized to intramuscular naloxone administration were less likely to require a rescue dose of naloxone compared with clients randomized to intranasal naloxone administration (8 [8.6%] vs 24 [23.1%]; odds ratio, 0.35; 95% CI, 0.15-0.66; P = .002). A 65% increase in hazard (hazard ratio, 1.65; 95% CI, 1.21-2.25; P = .002) for time to respiratory rate of at least 10 and an 81% increase in hazard (hazard ratio, 1.81; 95% CI, 1.28-2.56; P = .001) for time to Glasgow Coma Scale score of at least 13 were observed for the group receiving intranasal naloxone compared with the group receiving intramuscular naloxone. No major adverse events were reported for either group.

CONCLUSIONS AND RELEVANCE

This trial showed that intranasally administered naloxone in a supervised injecting facility can reverse opioid overdose but not as efficiently as intramuscularly administered naloxone can, findings that largely replicate those of previous unblinded clinical trials. These results suggest that determining the optimal dose and concentration of intranasal naloxone to respond to opioid overdose in real-world conditions is an international priority.

TRIAL REGISTRATION

anzctr.org.au Identifier: ACTRN12611000852954.

The Role of Dynorphin and the Kappa Opioid Receptor in the Symptomatology of Schizophrenia: A Review of the Evidence

Schizophrenia is a debilitating mental illness that affects approximately 1% of the world's population. Despite much research in its neurobiology to aid in developing new treatments, little progress has been made. One system that has not received adequate attention is the kappa opioid system and its potential role in the emergence of symptoms, as well as its therapeutic potential. Here we present an overview of the kappa system and review various lines of evidence derived from clinical studies for dynorphin and kappa opioid receptor involvement in the pathology of both the positive and negative symptoms of schizophrenia. This overview includes evidence for the psychotomimetic effects of kappa opioid receptor agonists in healthy volunteers and their reversal by the pan-opioid antagonists naloxone and naltrexone and evidence for a therapeutic benefit in schizophrenia for 4 pan-opioid antagonists. We describe the interactions between kappa opioid receptors and the dopaminergic pathways that are disrupted in schizophrenia and the histologic evidence suggesting abnormal kappa opioid receptor signaling in schizophrenia. We conclude by discussing future directions.

Pharmacokinetics and pharmacodynamics of intranasal and intravenous naloxone hydrochloride administration in healthy dogs

OBJECTIVE

To evaluate the pharmacokinetics and pharmacodynamics of naloxone hydrochloride in dogs following intranasal (IN) and IV administration.

ANIMALS

6 healthy adult mixed-breed dogs.

PROCEDURES

In a blinded crossover design involving 2 experimental periods separated by a washout period (minimum of 7 days), dogs were randomly assigned to receive naloxone IN (4 mg via a commercially available fixed-dose naloxone atomizer; mean ± SD dose, 0.17 ± 0.02 mg/kg) or IV (0.04 mg/kg) in the first period and then the opposite treatment in the second period. Plasma naloxone concentrations, dog behavior, heart rate, and respiratory rate were evaluated for 24 hours/period.

RESULTS

Naloxone administered IN was well absorbed after a short lag time (mean ± SD, 2.3 ± 1.4 minutes). Mean maximum plasma concentration following IN and IV administration was 9.3 ± 2.5 ng/mL and 18.8 ± 3.9 ng/mL, respectively. Mean time to maximum concentration following IN administration was 22.5 ± 8.2 minutes. Mean terminal half-life after IN and IV administration was 47.4 ± 6.7 minutes and 37.0 ± 6.7 minutes, respectively. Mean bioavailability of naloxone administered IN was 32 ± 13%. There were no notable changes in dog behavior, heart rate, or respiratory rate following naloxone administration by either route.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of a naloxone atomizer for IN naloxone administration in dogs may represent an effective alternative to IV administration in emergency situations involving opioid exposure. Future studies are needed to evaluate the efficacy of IN naloxone administration in dogs with opioid intoxication, including a determination of effective doses.

One single large intramuscular dose of naloxone is effective and safe in suspected heroin poisoning

OBJECTIVE

Naloxone is an established antidote for the treatment of heroin poisoning; however, dosing regimens vary widely, with a current trend towards small titrated intravenous dosing. This study aims to characterise naloxone use in the treatment of patients presenting with suspected heroin poisoning.

METHODS

This was a retrospective review of poisoned patients presenting to a clinical toxicology unit in Brisbane from January 2015 to December 2017. Patient demographics, clinical effects, naloxone dosing, observation periods and complications were extracted from the patient's medical records.

RESULTS

There were 117 presentations accounted for by 108 patients. Prehospital naloxone was provided to 57 (49%) patients, 46 of which received a standardised 1.6 mg i.m. dose. The remaining 60 (51%) patients received their first naloxone in hospital, with 58 (97%) receiving this by titrated i.v. doses. A subsequent naloxone infusion was required significantly more often in those treated with i.v. titrated naloxone compared to i.m. dose (27/69 [39%] vs 5/48 [10%], P = 0.0006). The need for parenteral sedation to manage acute behavioural disturbance following naloxone provision was rare (3/117 [3%]).

CONCLUSIONS

In this retrospective observational study, a single large i.m. dose of naloxone reversed the toxicity of suspected heroin overdose in the majority of patients. In addition, patients were less likely to require repeated intermittent doses or naloxone infusion than those treated solely with i.v. naloxone. Further comparison in a prospective study is warranted to validate these observations in confirmed heroin overdose. Requirement for sedation secondary to acute behavioural disturbance was rare regardless of the route.

Intranasal therapy with opioids for children and adolescents with cancer: results from clinical studies

Opioids are essential for the treatment of pain, which is a serious symptom for children and adolescents affected by cancer. Intranasal opioids may be very useful for the treatment of breakthrough pain in children and adolescents with cancer, for their little invasiveness, ease of administration, rapid onset of action, and high bioavailability. Intranasal drug delivery may be influenced by anatomical and physiological factors (nasal mucosa absorption area, mucociliary clearance, enzymatic activity, anatomical anomalies, chronic or inflammatory alterations of nasal mucosa), drug-related factors (molecular weight, solubility), and delivery device. Fentanyl is a lipophilic opioid commonly proposed for intranasal use among pediatric patients, but no studies have been conducted yet about intranasal use of other available opioids for management of pediatric cancer pain. In this review, we analyze several elements which may influence absorption of intranasal opioids in children and adolescents, with a focus on pharmacokinetics and therapeutic aspects of each opioid currently available for intranasal use.

Prepacked naloxone administration for suspected opioid overdose in the era of illicitly manufactured fentanyl: a retrospective study of regional poison center data

Background: Prepacked naloxone kits (PNKs) are frequently used to reverse opioid intoxication. It is unknown if the presence of illicitly manufactured fentanyl and its analogs (IMFs) in heroin supply is affecting the PNK doses given by laypersons. We investigated the trend of PNK dose administered to reverse opioid toxicity in suspected/undifferentiated opioid intoxication.Methods: We retrospectively reviewed PNK administrations reported to the Maryland Poison Center between 1 January 2015 and 15 October 2017. Primary outcome was the mean PNK dose administered to reverse opioid-induced central nervous system and ventilatory depression. Secondary outcomes included the reversal rate of opioid toxicity, patient disposition, and survival rate.Results: Our analysis involved 1139 PNK administrations. The mean age of subjects was 34.3 years; 68.8% (n = 781) were male. Ventilatory depression was present in 98.2% (n = 958) of cases, and 97% (n = 1097) were unresponsive. Law enforcement administered the majority of PNK (91.0%; n = 1035); the primary route was intranasal (97.9%; n = 1051). Toxicity was reversed in 79.2% (n = 886) of overdose victims after a mean PNK dose of 3.12 mg. EMS personnel gave 291 subjects additional naloxone (mean: 2.2 mg), reversing opioid toxicity in 94.2% (n = 254). Between 2015 and 2017, the mean PNK dose increased from 2.12 to 3.63 mg (p < .0001) while the reversal rate decreased from 82.1% to 76.4% (p = .04). One hundred and eighty-two patients (15.9%) refused transport; of those transported to a hospital, 73.4% (n = 569) were treated and released and 12.4% (n = 96) required hospitalization. Ninety-six percent (n = 1092) of the subjects survived. Forty subjects were pronounced dead at the scene. Fentanyl or its analog was detected in 36 of 55 opioid-related deaths (65.5%).Conclusions: PNK administration reversed toxicity in the majority of patients with undifferentiated opioid intoxication. Between 2015 and 2017, increasing doses of PNK were administered but the reversal rate decreased. These trends are likely multifactorial, including increasing availability of IMFs.

Simultaneous quantification of high-dose naloxone and naloxone-3-β-d-glucuronide in human plasma by UHPLC-MS/MS

Aim: High-dose administration of the μ-opioid receptor inverse agonist naloxone (NX), has previously been demonstrated to reinstate nocifensive behavior in the late phase of inflammatory injuries. However, no current analytical methods can provide pharmacokinetic insight into the pharmacodynamic response of high-dose administration of NX. Materials & methods: Based on protein precipitation using 50 μl human plasma, NX and naloxone-β-d-glucuronide (NXG) was analysed by UHPLC-MS/MS with 6 min cycle time. Results: A method for quantification of high-dose administered NX and NXG was developed and validated with intra- and interday precision and accuracy within ≤8.5% relative standard deviation (RSD) and -1.2-5.5% relative error (RE) for NX and ≤9.6% RSD and 0.6-6.5% RE for NXG. The method show excellent internal standard corrected matrix effects. Conclusion: A rapid UHPLC-MS/MS method was developed for quantification of NX and NXG in human plasma within 10-4000 ng/ml.

High-dose naloxone, an experimental tool uncovering latent sensitisation: pharmacokinetics in humans

BACKGROUND

Naloxone, an opioid receptor antagonist, is used as a pharmacological tool to detect tonic endogenous activation of opioid receptors in experimental pain models. We describe a pharmacokinetic model linking naloxone pharmacokinetics to its main metabolite after high-dose naloxone infusion.

METHODS

Eight healthy volunteers received a three-stage stepwise high-dose i.v. naloxone infusion (total dose 3.25 mg kg^-1). Naloxone and naloxone-3-glucuronide (N3G) plasma concentrations were sampled from infusion onset to 334 min after infusion discontinuation. Pharmacokinetic analysis was performed using non-linear mixed effect models (NONMEM). The predictive performances of Dowling's and Yassen's models were evaluated, and target-controlled infusion simulations were performed.

RESULTS

Three- and two-compartment disposition models with linear elimination kinetics described the naloxone and N3G concentration time-courses, respectively. Two covariate models were developed: simple (weight proportional) and complex (with the shallow peripheral volume of distribution linearly increasing with body weight). The median prediction error (MDPE) and wobble for Dowling's model were -32.5% and 33.4%, respectively. For Yassen's model, the MDPE and wobble were 1.2% and 19.9%, respectively.

CONCLUSIONS

A parent-metabolite pharmacokinetic model was developed for naloxone and N3G after high-dose naloxone infusion. No saturable pharmacokinetics were observed. Whereas Dowling's model was inaccurate and over-predicted naloxone concentrations, Yassen's model accurately predicted naloxone pharmacokinetics. The newly developed covariate models may be used for high-dose TCI-naloxone for experimental and clinical practice.

CLINICAL TRIALS REGISTRATION

NCT01992146.

The pharmacokinetics of intranasal droperidol in volunteers characterised via population modelling

Background

Droperidol is used parenterally to treat nausea and vomiting, migraine and acute behavioural disturbance. Intranasal use is not reported for droperidol. Intranasal drug administration reduces need for intravenous line placement and risk of needle-stick.

Objective

To model population pharmacokinetics of intranasal droperidol.

Method

Single doses of intranasal and intravenous droperidol (0.02 mg/kg) were studied in an open-label crossover-trial in seven volunteers with a 1-week washout period. Blood samples collected over 10-h were analysed by liquid chromatography tandem mass spectrometer. Droperidol plasma concentrations following intravenous and intranasal administration were subjected to non-compartmental analysis and population pharmacokinetic modelling using S-ADAPT. Monte Carlo simulations were conducted for various potential intranasal dosage regimens.

Results

The droperidol concentration-time profiles following intravenous and intranasal administration were best described by a model with two equilibrating disposition compartments and linear elimination. The apparent elimination clearance for intranasal dosing was 87.9 L/h and apparent central volume of distribution 18.2 L. Monte Carlo simulations of 5 mg droperidol (corresponding to the maximum volume that can be practically administered intranasal at a time) given intranasally at 0 and 5 min or 0 and 10 min indicated peak concentrations would reach those seen at 25 min after single intravenous administration of 1.5 mg. No adverse clinical effects or QT interval prolongation were observed.

Conclusion

Given the reduced bioavailability of intranasal droperidol, Monte Carlo simulations suggested that it could potentially be used at a higher dose (2.5-5 mg) than currently used intravenously in clinical trials assessing the effectiveness in treatment of nausea, vomiting and migraine.

Pharmacokinetic properties of intranasal and injectable formulations of naloxone for community use: a systematic review

Aim: To assess the pharmacokinetic properties of community-use formulations of naloxone for emergency treatment of opioid overdose. Methods: Systematic literature review based on searches of established databases and congress archives. Results: Seven studies met inclusion criteria: two of US FDA-approved intramuscular (im.)/subcutaneous (sc.) auto-injectors, one of an FDA-approved intranasal spray, two of unapproved intranasal kits (syringe with atomizer attachment) and two of intranasal products in development. Conclusion: The pharmacokinetics of im./sc. auto-injector 2 mg and approved intranasal spray (2 and 4 mg) demonstrated rapid uptake and naloxone exposure exceeding that of the historic benchmark (0.4 mg im.), indicating that naloxone exposure was adequate for reversal of opioid overdose.

Post-stroke Intranasal (+)-Naloxone Delivery Reduces Microglial Activation and Improves Behavioral Recovery from Ischemic Injury

Ischemic stroke is the leading cause of disability, and effective therapeutic strategies are needed to promote complete recovery. Neuroinflammation plays a significant role in stroke pathophysiology, and there is limited understanding of how it affects recovery. The aim of this study was to characterize the spatiotemporal expression profile of microglial activation and whether dampening microglial/macrophage activation post-stroke facilitates the recovery. For dampening microglial/macrophage activation, we chose intranasal administration of naloxone, a drug that is already in clinical use for opioid overdose and is known to decrease microglia/macrophage activation. We characterized the temporal progression of microglia/macrophage activation following cortical ischemic injury in rat and found the peak activation in cortex 7 d post-stroke. Unexpectedly, there was a chronic expression of phagocytic cells in the thalamus associated with neuronal loss. (+)-Naloxone, an enantiomer that reduces microglial activation without antagonizing opioid receptors, was administered intranasally starting 1 d post-stroke and continuing for 7 d. (+)-Naloxone treatment decreased microglia/macrophage activation in the striatum and thalamus, promoted behavioral recovery during the 14-d monitoring period, and reduced neuronal death in the lesioned cortex and ipsilateral thalamus. Our results are the first to show that post-stroke intranasal (+)-naloxone administration promotes short-term functional recovery and reduces microglia/macrophage activation. Therefore, (+)-naloxone is a promising drug for the treatment of ischemic stroke, and further studies should be conducted.

Pharmacokinetics and -dynamics of intramuscular and intranasal naloxone: an explorative study in healthy volunteers

PURPOSE

This study aimed to develop a model for pharmacodynamic and pharmacokinetic studies of naloxone antagonism under steady-state opioid agonism and to compare a high-concentration/low-volume intranasal naloxone formulation 8 mg/ml to intramuscular 0.8 mg.

METHODS

Two-way crossover in 12 healthy volunteers receiving naloxone while receiving remifentanil by a target-controlled infusion for 102 min. The group were subdivided into three different doses of remifentanil. Blood samples for serum naloxone concentrations, pupillometry and heat pain threshold were measured.

RESULTS

The relative bioavailability of intranasal to intramuscular naloxone was 0.75. Pupillometry showed difference in antagonism; the effect was significant in the data set as a whole (p < 0.001) and in all three subgroups (p < 0.02-p < 0.001). Heat pain threshold showed no statistical difference.

CONCLUSIONS

A target-controlled infusion of remifentanil provides good conditions for studying the pharmacodynamics of naloxone, and pupillometry was a better modality than heat pain threshold. Intranasal naloxone 0.8 mg is inferior for a similar dose intramuscular. Our design may help to bridge the gap between studies in healthy volunteers and the patient population in need of naloxone for opioid overdose.

TRIAL REGISTRATION

clinicaltrials.gov : NCT02307721.

Pharmacokinetics of concentrated naloxone nasal spray for opioid overdose reversal: Phase I healthy volunteer study

BACKGROUND AND AIMS

Take-home naloxone can prevent death from heroin/opioid overdose, but pre-provision is difficult because naloxone is usually given by injection. Non-injectable alternatives, including naloxone nasal sprays, are currently being developed. To be effective, the intranasal (i.n.) spray dose must be adequate but not excessive, and early absorption must be comparable to intramuscular (i.m.) injection. We report on the pharmacokinetics (PK) of a specially produced concentrated novel nasal spray. The specific aims were to: (1) estimate PK profiles of i.n. naloxone, (2) compare early systemic exposure with i.n. versus i.m. naloxone and (3) estimate i.n. bioavailability.

DESIGN

Open-label, randomized, five-way cross-over PK study.

SETTING

Clinical trials facility (Croydon, UK).

PARTICIPANTS

Thirty-eight healthy volunteers (age 20-54 years; 11 female).

INTERVENTION AND COMPARATOR

Three doses of i.n. (1 mg/0.1 ml, 2 mg/0.1 ml, 4 mg/0.2 ml) versus 0.4 mg i.m. (reference) and 0.4 mg intravenous (i.v.) naloxone.

MEASUREMENTS

Regular blood samples were taken, with high-frequency sampling during the first 15 minutes to capture early systemic exposure. PK parameters were determined from plasma naloxone concentrations. Exploratory analyses involved simulation of repeat administration.

FINDINGS

Mean peak concentration (C_max ) values for 1 mg (1.51 ng/ml), 2 mg (2.87 ng/ml) and 4 mg (6.02 ng/ml) i.n. exceeded 0.4 mg i.m. (1.27 ng/ml) naloxone. All three i.n. doses rapidly achieved plasma levels > 50% of peak concentrations (T50%) by 10 minutes, peaking at 15-30 minutes (T_max ). For comparison, the i.m. reference reached T_max at 10 minutes. Mean bioavailability was 47-51% for i.n. relative to i.m. naloxone. Simulation of repeat dosing (2 × 2 mg i.n. versus 5 × 0.4 mg i.m. doses) at 3-minute intervals showed that comparable plasma naloxone concentrations would be anticipated.

CONCLUSIONS

Concentrated 2 mg intranasal naloxone is well-absorbed and provides early exposure comparable to 0.4 mg intramuscular naloxone, following the 0.4 mg intramuscular curve closely in the first 10 minutes post-dosing and maintaining blood levels above twice the intramuscular reference for the next 2 hours.

Naloxone dosage for opioid reversal: current evidence and clinical implications

Opioid-related mortality is a growing problem in the United States, and in 2015 there were over 33,000 opioid-related deaths. To combat this mortality trend, naloxone is increasingly being utilized in a pre-hospital setting by emergency personnel and prescribed to laypersons for out-of-hospital administration. With increased utilization of naloxone there has been a subsequent reduction in mortality following an opioid overdose. Reversal of opioid toxicity may precipitate an opioid-withdrawal syndrome. At the same time, there is a risk of inadequate response or re-narcotization after the administration of a single dose of naloxone in patients who have taken large doses or long-acting opioid formulations, as the duration of effect of naloxone is shorter than that of many opioid agonists. As out-of-hospital use of this medication is growing, so too is concern about effective but safe dosing.

Intranasal naloxone and related strategies for opioid overdose intervention by nonmedical personnel: a review

Deaths due to prescription and illicit opioid overdose have been rising at an alarming rate, particularly in the USA. Although naloxone injection is a safe and effective treatment for opioid overdose, it is frequently unavailable in a timely manner due to legal and practical restrictions on its use by laypeople. As a result, an effort spanning decades has resulted in the development of strategies to make naloxone available for layperson or "take-home" use. This has included the development of naloxone formulations that are easier to administer for nonmedical users, such as intranasal and autoinjector intramuscular delivery systems, efforts to distribute naloxone to potentially high-impact categories of nonmedical users, as well as efforts to reduce regulatory barriers to more widespread distribution and use. Here we review the historical and current literature on the efficacy and safety of naloxone for use by nonmedical persons, provide an evidence-based discussion of the controversies regarding the safety and efficacy of different formulations of take-home naloxone, and assess the status of current efforts to increase its public distribution. Take-home naloxone is safe and effective for the treatment of opioid overdose when administered by laypeople in a community setting, shortening the time to reversal of opioid toxicity and reducing opioid-related deaths. Complementary strategies have together shown promise for increased dissemination of take-home naloxone, including 1) provision of education and training; 2) distribution to critical populations such as persons with opioid addiction, family members, and first responders; 3) reduction of prescribing barriers to access; and 4) reduction of legal recrimination fears as barriers to use. Although there has been considerable progress in decreasing the regulatory and legal barriers to effective implementation of community naloxone programs, significant barriers still exist, and much work remains to be done to integrate these programs into efforts to provide effective treatment of opioid use disorders.

Pharmacokinetics of concentrated naloxone nasal spray over first 30 minutes post-dosing: analysis of suitability for opioid overdose reversal

BACKGROUND AND AIMS

Lack of non-injectable naloxone formulations has impeded widespread take-home provision for the prevention of heroin/opioid overdose deaths. For non-injectable formulations that are finally being investigated, rapid onset of action and sufficient bioavailability will be vital. We present analysis of data from a study of concentrated naloxone nasal spray formulations. Our aims are: to assess (1) pharmacokinetic properties and (2) suitability for overdose reversal in terms of naloxone absorption within 30 minutes post-dosing.

DESIGN AND INTERVENTIONS/COMPARATOR

Open-label, randomized, four-way cross-over Latin-square pharmacokinetic study of naloxone administration by three routes: intranasal at two doses (8 mg/0.4 ml, 16 mg/0.4 ml) versus sublingual (16 mg/ml) versus intravenous reference (1 mg/ml).

SETTING

Clinical Pharmacology Unit at The Ohio State University (Columbus, OH, USA).

PARTICIPANTS

Twelve healthy volunteers (age 20-41; seven female).

MEASUREMENTS

From blood plasma naloxone concentrations, (1) standard pharmacokinetic parameters, including maximum plasma concentration (C_max ) and mean absolute bioavailability (F%, relative to intravenous injection), were determined; as well as (2) partial area under the curve (AUC) values, t_max (time to maximum plasma concentration) and t_50% (time to 50% of maximum plasma concentration) as measures of early absorption.

FINDINGS

(1) Bioavailability was F% = 25-28% for intranasal naloxone. Sublingual had low bioavailability (F% = 2%) and was not considered further. Mean C_max values for 8 mg (12.83 ng/ml) and 16 mg (18.25 ng/ml) intranasal exceeded 1 mg intravenous (9.64 ng/ml) naloxone. (2) Following intranasal administration, t_50% was reached within 8 minutes and t_max within 20 minutes. Mean naloxone absorption from dosing to 30 minutes (AUC₃₀ ) was greater following 8 mg (4.17 h × ng/ml) and 16 mg (5.91 h × ng/ml) intranasal than following 1 mg intravenous (1.70 h × ng/ml) administration.

CONCLUSIONS

Concentrated naloxone nasal spray has a promising pharmacokinetic profile, with substantial bioavailability. Its early absorption time-course suggests that concentrated nasal naloxone is suitable for emergency administration in the community, where rapid restoration of respiratory function is essential for opioid overdose reversal.

Multiple Naloxone Administrations Among Emergency Medical Service Providers is Increasing

BACKGROUND

Opioid overdoses are at epidemic levels in the United States. Emergency Medical Service (EMS) providers may administer naloxone to restore patient breathing and prevent respiratory arrest. There was a need for contemporary data to examine the number of naloxone administrations in an EMS encounter.

METHODS

Using data from the National Emergency Medical Services Information System, we examined data from 2012-5 to determine trends in patients receiving multiple naloxone administrations (MNAs). Logistic regression including demographic, clinical, and operational information was used to examine factors associated with MNA.

RESULTS

Among all events where naloxone was administered only 16.7% of the 911 calls specifically identified the medical emergency as a drug ingestion or poisoning event. The percentage of patients receiving MNA increased from 14.5% in 2012 to 18.2% in 2015, which represents a 26% increase in MNA in 4 years. Patients aged 20-29 had the highest percentage of MNA (21.1%). Patients in the Northeast and the Midwest had the highest relative MNA (Chi Squared = 539.5, p < 0.01 and Chi Squared = 351.2, p < 0.01, respectively). The logistic regression model showed that the adjusted odds ratios (aOR) for MNA were greatest among people who live in the Northeast (aOR = 1.18, 95% CI = 1.13-1.22) and for men (aOR = 1.13, 95% CI = 1.10-1.16), but lower for suburban and rural areas (aOR = 0.76, 95% CI = 0.72-0.80 and aOR = 0.85, 95% CI = 0.80-0.89) and lowest for wilderness areas (aOR = 0.76, 95% CI = 0.68-0.84). Higher adjusted odds of MNA occurred when an advanced life support (ALS 2) level of service was provided compared to basic life support (BLS) ambulances (aOR = 2.15, 95% CI = 1.45-3.16) and when the dispatch complaint indicated there was a drug poisoning event (aOR = 1.12, 95% CI = 1.09-1.16). Reported layperson naloxone administration prior to EMS arrival was rare (1%).

CONCLUSION

This study shows that frequency of MNA is growing over time and is regionally dependent. MNA may be a barometer of the potency of the opioid involved in the overdose. The increase in MNA provides support for a dosage review. Better identification of opioid related events in the dispatch system could lead to a better match of services with patient needs.

Pharmacokinetics after a single dose of naloxone administered as a nasal spray in healthy volunteers

BACKGROUND

There is increasing interest in the use of intranasal naloxone to reverse adverse opioid effects during management of procedural pain in children and in adults after overdose. There are limited data on the pharmacokinetics of intranasal naloxone so in this study we aimed to detail the pharmacokinetic profile of the commercially marketed injectable solution of naloxone 0.4 mg/ml when administered as an intranasal spray.

METHODS

Twenty healthy volunteers received naloxone as an intranasal spray at a dose of 10 μg/kg. Venous blood sampling was carried out for 90 min after administration to determine the time profile of the plasma concentrations of using tandem mass spectrometry. Pharmacokinetic parameters were calculated using a one-compartment model.

RESULTS

Median time to maximum naloxone concentration (Tmax) was 14.5 (95% CI: 9.0-16.5) min, mean maximum naloxone concentration (Cmax) was 1.09 ± 0.56 ng/ml and mean AUC_{0-90 min} was 37.1 ± 15.0 ng*min/ml. Elimination half-life estimated from the median concentration data was 28.2 min.

CONCLUSION

Our results show a faster uptake of intranasal naloxone to maximum concentration compared with previous studies although with a marked variation in maximum concentration. The findings are consistent with our clinical experience of the time profile for reversing the effects of sufentanil sedation in children.

International patent applications for non-injectable naloxone for opioid overdose reversal: Exploratory search and retrieve analysis of the PatentScope database

ISSUES

Non-injectable naloxone formulations are being developed for opioid overdose reversal, but only limited data have been published in the peer-reviewed domain. Through examination of a hitherto-unsearched database, we expand public knowledge of non-injectable formulations, tracing their development and novelty, with the aim to describe and compare their pharmacokinetic properties.

APPROACH

(i) The PatentScope database of the World Intellectual Property Organization was searched for relevant English-language patent applications; (ii) Pharmacokinetic data were extracted, collated and analysed; (iii) PubMed was searched using Boolean search query '(nasal OR intranasal OR nose OR buccal OR sublingual) AND naloxone AND pharmacokinetics'.

KEY FINDINGS

Five hundred and twenty-two PatentScope and 56 PubMed records were identified: three published international patent applications and five peer-reviewed papers were eligible. Pharmacokinetic data were available for intranasal, sublingual, and reference routes. Highly concentrated formulations (10-40 mg mL^-1 ) had been developed and tested. Sublingual bioavailability was very low (1%; relative to intravenous). Non-concentrated intranasal spray (1 mg mL^-1 ; 1 mL per nostril) had low bioavailability (11%). Concentrated intranasal formulations (≥10 mg mL^-1 ) had bioavailability of 21-42% (relative to intravenous) and 26-57% (relative to intramuscular), with peak concentrations (dose-adjusted C_max  = 0.8-1.7 ng mL^-1 ) reached in 19-30 min (t_max ).

IMPLICATIONS

Exploratory analysis identified intranasal bioavailability as associated positively with dose and negatively with volume.

CONCLUSION

We find consistent direction of development of intranasal sprays to high-concentration, low-volume formulations with bioavailability in the 20-60% range. These have potential to deliver a therapeutic dose in 0.1 mL volume. [McDonald R, Danielsson Glende Ø, Dale O, Strang J. International patent applications for non-injectable naloxone for opioid overdose reversal: Exploratory search and retrieve analysis of the PatentScope database. Drug Alcohol Rev 2017;00:000-000].

Comparison of a New Intranasal Naloxone Formulation to Intramuscular Naloxone: Results from Hypothesis-generating Small Clinical Studies

Easy‐to‐use naloxone formulations are needed to help address the opioid overdose epidemic. The pharmacokinetics of i.v., i.m., and a new i.n. naloxone formulation (2 mg) were compared in six healthy volunteers. Relative to i.m. naloxone, geometric mean (90% confidence interval [CI]) absolute bioavailability of i.n. naloxone was modestly lower (55%; 90% CI, 43–70% vs. 41%; 90% CI, 27–62%), whereas average (±SE) mean absorption time was substantially shorter (74 ± 8.8 vs. 6.7 ± 4.9 min). The opioid‐attenuating effects of i.n. naloxone were compared with i.m. naloxone (2 mg) after administration of oral alfentanil (4 mg) to a separate group of six healthy volunteers pretreated with 240 mL of water or grapefruit juice. The i.m. and i.n. naloxone attenuated miosis by similar extents after water (40 ± 15 vs. 41 ± 21 h*%) and grapefruit juice (49 ± 18 vs. 50 ± 22 h*%) pretreatment. Results merit further testing of this new naloxone formulation.

When to Pick the Nose: Out-of-Hospital and Emergency Department Intranasal Administration of Medications

The intranasal route for medication administration is increasingly popular in the emergency department and out-of-hospital setting because such administration is simple and fast, and can be used for patients without intravenous access and in situations in which obtaining an intravenous line is difficult or time intensive (eg, for patients who are seizing or combative). Several small studies (mostly pediatric) have shown midazolam to be effective for procedural sedation, anxiolysis, and seizures. Intranasal fentanyl demonstrates both safety and efficacy for the management of acute pain. The intranasal route appears to be an effective alternative for naloxone in opioid overdose. The literature is less clear on roles for intranasal ketamine and dexmedetomidine.

Pharmacokinetics of a new, nasal formulation of naloxone

PURPOSE

Nasal naloxone is wanted for bystander administration in opioid overdose and as a needle-free alternative for emergency medical personnel. Epidemiologic studies have indicated a therapeutic effect of bystander administration of low-concentration/high-volume formulations. The objective for this study was to describe the nasal pharmacokinetics of a new high-concentration/low-volume nasal formulation of naloxone.

METHODS

This was an open, randomized triple crossover trial in healthy, human volunteers (n = 12) where two doses of nasal naloxone (0.8 and 1.6 mg) and one intravenous dose (1.0 mg) were compared. Fifteen serum samples were collected before and until 6 h after naloxone administration. Quantification of naloxone was performed by a validated liquid chromatography-tandem mass spectrometry method.

RESULTS

Bioavailability was 0.54 (0.45-0.63) for the 0.8 mg and 0.52 (0.37-0.67) for the 1.6 mg nasal naloxone formulation. Maximum concentration levels (C _max) were 1.45 ng/ml (1.07-1.84) for 0.8 mg and 2.57 ng/ml (1.49-3.66) for the 1.6 mg. Time to maximum concentrations (T _max) were reached at 17.9 min (11.4-24.5) and 18.6 min (14.4-22.9) for the 0.8 mg and the 1.6 mg doses, respectively.

CONCLUSION

This nasal naloxone formulation had a rapid, systemic uptake and higher bioavailability than naloxone formulations not designed for IN use. This indicates that an optimized high-concentration/low-volume nasal spray formulation may deliver a therapeutic dose. The 1.6 mg nasal dose provided serum concentrations that surpassed those of 1.0 mg IV after 15-20 min and stayed above for the rest of the study period.

Challenges and Opportunities with Predicting in Vivo Phase II Metabolism via Glucuronidation from in Vitro Data

Glucuronidation is the most important phase II metabolic pathway which is responsible for the clearance of many endogenous and exogenous compounds. To better understand the elimination process for compounds undergoing glucuronidation and identify compounds with desirable in vivo pharmacokinetic properties, many efforts have been made to predict in vivo glucuronidation using in vitro data. In this article, we reviewed typical approaches used in previous predictions. The problems and challenges in prediction of glucuronidation were discussed. Besides that different incubation conditions can affect the prediction accuracy, other factors including efflux / uptake transporters, enterohepatic recycling, and deglucuronidation reactions also contribute to the disposition of glucuronides and make the prediction more difficult. PBPK modeling, which can describe more complicated process in vivo, is a promising prediction strategy which may greatly improve the prediction of glucuronidation and potential DDIs involving glucuronidation. Based on previous studies, we proposed a transport-glucuronidation classification system, which was built based on the kinetics of both glucuronidation and transport of the glucuronide. This system could be a very useful tool to achieve better in vivo predictions.

Effects of target-controlled infusion of high-dose naloxone on pain and hyperalgesia in a human thermal injury model: a study protocol: A randomized, double-blind, placebo-controlled, crossover trial with an enriched design

Mu-opioid-receptor antagonists have been extensively studied in experimental research as pharmacological tools uncovering mechanisms of pain modulation by the endogenous opioid system. In rodents, administration of high doses of mu-opioid-receptor antagonists after the resolution of an inflammatory injury has demonstrated reinstatement of nociceptive hypersensitivity indicating unmasking of latent sensitization. In a recent human study, pain hypersensitivity assessed as secondary hyperalgesia area (SHA), was reinstated 7 days after a mild thermal injury, in 4 out of 12 subjects after a naloxone infusion.The aims of the present study are first, to replicate our previous findings in a larger-sized study; second, to examine if high sensitizers (subjects presenting with large SHA after a thermal injury) develop a higher degree of hypersensitivity after naloxone challenge than low sensitizers (subjects presenting with restricted SHA after a thermal injury); and third to examine a dose-response relationship between 3 stable naloxone concentrations controlled by target-controlled infusion, and the unmasking of latent sensitization.Healthy participants (n = 80) underwent a screening day (day 0) with induction of a thermal skin injury (47°C, 420 seconds, 12.5 cm). Assessment of SHA was performed 1 and 2 hours after the injury. Using an enriched design, only participants belonging to the upper quartile of SHA (Q4, high sensitizers; n = 20) and the lower quartile of SHA (Q1, low sensitizers; n = 20) continued the study, comprising 4 consecutive days-days 1 to 4. Thermal skin injuries were repeated on day 1 and day 3, whereas day 2 and day 4 (7 days after day 1 and day 3, respectively) were target-controlled infusion days in which the subjects were randomly allocated to receive either naloxone (3.25 mg/kg, 4 mg/mL) or placebo (normal saline) intravenous. The primary outcome was SHA assessed by weighted-pin instrument (128 mN) 0, 1, 2, and 165 to 169 hours after the thermal injury (day 1-4). The secondary outcomes were pin-prick pain thresholds assessed by weighted-pin instrument (8-512 mN) at primary and secondary hyperalgesia areas (days 1-4).The naloxone-induced unmasking of latent sensitization is an interesting model for exploring the transition from acute to chronic pain. The results from the present study may provide valuable information regarding future research in persistent postsurgical pain states.

Take-home naloxone treatment for opioid emergencies: a comparison of routes of administration and associated delivery systems

INTRODUCTION

Naloxone reversal of opioid-induced respiratory depression outside of medical facilities has become more prevalent because of the escalating opioid epidemic in the USA. Take-home naloxone for treatment of opioid emergencies is now being recommended by numerous federal, state, and professional organizations. Areas covered: The scope of the opioid overdose epidemic is reviewed along with practical, clinical, regulatory, and usability considerations for take-home naloxone routes of administration currently available and associated delivery systems. Specific opioid-related factors are discussed in detail with emphasis placed on life-threatening respiratory depression and naloxone antagonism. A clinical overview, including pharmacokinetic and FDA approval information for each take-home naloxone product is discussed in detail as well as the impact of take-home naloxone in the community. Finally, given these products are to be used in a panic-stricken, life-threatening opioid emergency, an analysis of available usability data is provided with proposed directions for further study. Expert opinion: Based on the available clinical evidence, auto-injectable naloxone should be the preferred administration route for take-home naloxone treatment until additional safety, efficacy, and comparative outcomes data are available for unconventional routes of administration that unequivocally provide equal or superior results.

Intranasal Opioid Administration in Rhesus Monkeys: PET Imaging and Antinociception

The goal of this study was to evaluate the effects of intranasally administered opioids in rhesus monkeys using the tail-withdrawal assay, and to correlate these effects with measures of receptor occupancy using positron emission tomography (PET) imaging. Initial experiments characterized the antinociceptive effects of intranasal (IN) fentanyl and buprenorphine relative to intramuscular (IM) injection. Fentanyl (0.010-0.032 mg/kg) and buprenorphine (0.1-1.0 mg/kg) produced dose-dependent increases in tail-withdrawal latency that did not differ between routes of delivery. The second experiment compared the ability of IN and intravenous (IV) naloxone (NLX) to block the antinociceptive effects IV fentanyl, and to measure receptor occupancy at equipotent doses of NLX using PET imaging. IN and IV NLX (0.0032-0.032 mg/kg) produced dose-dependent decreases in fentanyl-induced antinociception. Again, there was no difference observed in overall potency between routes. PET imaging showed that IV and IN NLX produced similar decreases in receptor occupancy as measured by [¹¹C]carfentanil blocking, although there was a trend for IV NLX to produce marginally greater occupancy changes. This study validated the first procedures to evaluate the IN effects of opioids in rhesus monkeys.